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A biomarker of doping indicates the biological response to the use of a prohibited substance or method. Uncovering novel biomarkers of doping is a key objective in order to improve antidoping outcomes such as the detection of doping and changing athlete behavior toward doping practices. While the antidoping field has been successful in validating novel metabolites of prohibited substances, there has been less success in developing new biomarkers of doping. Employing the most suitable study designs and analytical approaches is critical to successfully uncovering novel biomarkers of doping with a high potential for translation into routine analysis. Here we argue that the antidoping field is well positioned for biomarker discovery and outline considerations for the development of novel biomarkers of doping.

The systemic effect of glucocorticoids (GCs) following injectable routes of administration presents a potential risk to both improving performance and causing harm to health in athletes. This review evaluates the current GC antidoping regulations defined by the World Anti-Doping Agency and presents a novel approach for defining permitted and prohibited use of glucocorticoids in sport based on the pharmacological potential for performance enhancement (PE) and risk of adverse effects on health. Known performance-enhancing doses of glucocorticoids are expressed in terms of cortisol-equivalent doses and thereby the dose associated with a high potential for PE for any GC and route of administration can be derived. Consequently, revised and substance-specific laboratory reporting values are presented to better distinguish between prohibited and permitted use in sport. In addition, washout periods are presented to enable clinicians to prescribe glucocorticoids safely and to avoid the risk of athletes testing positive for a doping test.

Meldonium is a metabolic drug whose inclusion in the 2016 List of Prohibited Substances and Methods followed the analysis of data collected under the 2015 World Anti-Doping Agency Monitoring Program. In the early months of 2016, anti-doping laboratories reported an unusually high number of cases in which urine samples contained high concentrations of meldonium. Consequently, the meldonium excretion period in healthy athletes and the substance's long-term urine and blood (plasma) pharmacokinetics became central questions for the anti-doping community to address, to ensure appropriate assessment of the scientific and medical situation, and also fair treatment of athletes from a result management and legal standpoint. At the present time, data on meldonium pharmacokinetics is limited to a few studies, with no known data available on long-term excretion of high oral doses. The primary objective of this open-label study was to determine long-term urine and plasma pharmacokinetic parameters of meldonium in healthy volunteers. Study design included single and repeated functional load testing and assessment of L-carnitine administration on meldonium excretion and pharmacokinetics. Thirty-two volunteers were equally divided into two groups receiving either 1.0 g or 2.0 g of oral meldonium daily for 3 weeks. The study found meldonium takes several days to attain a steady state in blood and displays an elimination period over several months after cessation of treatment. Moreover, findings demonstrate that the daily dose, periodicity and duration of treatment with meldonium are the most important factors to consider in calculating the substance's elimination and complete body clearance.

Psychoactive substances have a long history of use as doping substances in sport, usually constituting the second most used drug class behind anabolic steroids. In addition to classic stimulants, a more disturbing problem is the increasing availability of novel psychoactive substances (NPS). The challenges faced by anti-doping authorities regarding these NPS are of the same kind as those experienced by public health authorities and law enforcement agencies. These include easy access to raw material for synthesis, rapid and worldwide dissemination of the products and difficulty to analytically characterize these unknown chemical entities and their metabolites. Information and resource sharing between the different parties concerned in detecting and curtailing the production, distribution and use of NPS, either from a health or anti-doping fields, should be encouraged to effectively counteract the use of NPS in society and sports.

The worldwide network of World Anti-Doping Agency (WADA)-accredited anti-doping laboratories plays a fundamental role in supporting the global fight against doping in sport. This role is dependent on the ability to provide accurate, reliable and comparable data in identifying and measuring the presence of prohibited substances and methods. The accredited laboratories participate in WADA’s External Quality Assessment Scheme (EQAS) program, which provides the structure to continuously assess and improve laboratory performance in compliance to the requirements of the International Standard for Laboratories and related Technical Documents. The WADA EQAS is comprised of various programs, including a blind EQAS, a double-blind EQAS and an educational EQAS, each with specific goals with regard to monitoring and improving laboratory competence. In this article, the anti-doping rules and processes that govern granting and maintenance of WADA laboratory accreditation, aimed at ensuring a high-quality of laboratory operations within the framework of the global fight against doping in sport, are reviewed.

This article provides a review of the leading role of the World Anti-Doping Agency (WADA) in the context of the global fight against doping in sport and the harmonization of anti-doping rules worldwide through the implementation of the World Anti-Doping Program. Particular emphasis is given to the WADA-laboratory accreditation program, which is coordinated by the Science Department of WADA in conjunction with the Laboratory Expert Group, and the cooperation with the international accreditation community through International Laboratory Accreditation Cooperation and other organizations, all of which contribute to constant improvement of laboratory performance in the global fight against doping in sport. A perspective is provided of the means to refine the existing anti-doping rules and programs to ensure continuous improvement in order to face growing sophisticated challenges. A viewpoint on WADA’s desire to embrace cooperation with other international organizations whose knowledge can contribute to the fight against doping in sport is acknowledged.

The List of Prohibited Substances and Methods (the List) is the International Standard that determines what is prohibited in sport in- and out-of-competition. The official text of the List is produced by the World Anti-Doping Agency (WADA), the international independent organization responsible for promoting, coordinating and monitoring the fight against doping in sport. The drafting of the annual List is a highly interactive and consultative process involving scientific and medical experts in anti-doping, sport federations and governments. In this article, the elements that compose the List as well as the process behind its annual revision and update are presented.

Due to its considered performance enhancing effects, human growth hormone (hGH) is abused as a doping agent in sport. Its misuse also carries potentially serious side effects to a person's health. Consequently, hGH and its releasing factors are prohibited in sport, as established in the Prohibited List which is updated and published yearly by the World Anti-Doping Agency (WADA). In order to fight the menace that hGH doping poses to the spirit of sport and to the health of athletes, the sport movement and the anti-doping authorities, initially led by the International Olympic Committee (IOC) and later by WADA, have put substantial efforts into developing tests for its detection. Currently, a primary analytical approach, the isoform differential immunoassay, has been implemented in WADA-accredited laboratories. In parallel, a second, indirect approach for the detection of hGH abuse, based on the quantification of hGH-associated biological markers, has been developed. The final aim is to combine both methodologies to improve the sensitivity and expand the time window to detect doping with hGH. In addition, novel analytical procedures, based on proteomic and genomic technologies as well as the use of mass spectrometry-based methods of detection, are being investigated for future application in hGH anti-doping tests.

Administration of recombinant human erythropoietin (rHumanEPO) improves sporting performance and hence is frequently subject to abuse by athletes, although rHumanEPO is prohibited by the WADA. Approaches to detect rHumanEPO doping have improved significantly in recent years but remain imperfect. A new transcriptomic-based longitudinal screening approach is being developed that has the potential to improve the analytical performance of current detection methods. In particular, studies are being funded by WADA to identify a 'molecular signature' of rHumanEPO doping and preliminary results are promising. In the first systematic study to be conducted, the expression of hundreds of genes were found to be altered by rHumanEPO with numerous gene transcripts being differentially expressed after the first injection and further transcripts profoundly upregulated during and subsequently downregulated up to 4 weeks postadministration of the drug; with the same transcriptomic pattern observed in all participants. The identification of a blood 'molecular signature' of rHumanEPO administration is the strongest evidence to date that gene biomarkers have the potential to substantially improve the analytical performance of current antidoping methods such as the Athlete Biological Passport for rHumanEPO detection. Given the early promise of transcriptomics, research using an 'omics'-based approach involving genomics, transcriptomics, proteomics and metabolomics should be intensified in order to achieve improved detection of rHumanEPO and other doping substances and methods difficult to detect such a recombinant human growth hormone and blood transfusions.

Prevention of the immediate excitotoxic phase occurring in response to spinal cord injury (SCI) is a major issue to reduce the neuronal damage responsible for any ensuing motor deficits. The present study evaluated the neuroprotective efficacy of three noncompetitive NMDA receptor antagonists: Gacyclidine (GK-11), a new compound, Dizocilpine (MK-801), and Cerestat (CNS-1102) in a rat spinal cord contusion model. To mimic human SCI, a standardized model of rat spinal cord closed contusion in which animals spontaneously and progressively recover from the induced paraplegia was employed. Such model, characterized by a slow recovery of hindlimb locomotor function enables easy quantification of the neuroprotection at both the behavioral and cellular level. The animals were treated intravenously with the respective drugs 10 min after the spinal contusion. The dose range study suggested that 1 mg/kg of Gacyclidine was the most effective dose to promote functional recovery in reducing by half the time needed to reach full locomotor recovery. Racemate and enantiomers of Gacyclidine showed similar neuroprotective effects, but treatment with the enantiomers were not as efficacious in promoting full functional recovery. Similarly, a prolonged treatment with the racemate was not as efficious as a single dose, suggesting that a prolonged blockade of the amino-excitatory neurotransmission may be deleterious. Finally, Dizocilpine and Cerestat treatments induced only a partial and delayed neuroprotective effect compared to Gacyclidine. Neuroprotection characterized by a reduction of the cystic cavity and of the astrogliosis was observed with all treatments. As Gacyclidine is already in clinical trials, the present findings suggest the premise that it is a promising agent for limiting the initial neuronal damage induced by CNS trauma leading to better functional recovery.

This article provides a brief perspective of the World Anti-Doping Agency (WADA) in the context of the fight against doping in sport and of the WADA Proficiency Testing Program as an essential element of the World Anti-Doping Program. The WADA Proficiency Testing Program exists within the framework of the WADA-accredited laboratories and is aimed at improving the effectiveness of the fight against doping by testing the ability of the laboratories to reliably identify and measure the substances and methods defined in the WADA Prohibited List. The paper provides an overview of the WADA Proficiency Testing scheme with respect to organization, test composition and evaluation of anti-doping methods and techniques. Scientific research is mentioned in the context of WADA’s involvement in generating reference materials for improvement of analytical activities of the WADA-accredited laboratories. WADA’s funding of a reference material for 19-norandrosterone in human urine is illustrated as an example.

Transient cerebral ischemia (5 min) releases unesterified fatty acids from membrane phospholipids, increasing brain concentrations of fatty acids for up to 1 h following reperfusion. To understand the reported anti-ischemic effect of Ginkgo biloba extract (EGb 761), we monitored its effect on brain fatty acid reincorporation in a gerbil-stroke model. Both common carotid arteries in awake gerbils were occluded for 5 min, followed by 5 min of reperfusion. Animals were infused intravenously with labeled arachidonic (AA) or palmitic acid (Pam), and rates of incorporation of unlabeled fatty acid from the brian acyl-CoA pool were calculated by the model of Robinson et al. (1992), using quantitative autoradiography and biochemical analysis of brain acyl-CoA. Animals were treated for 14 d with 50 or 150 mg/kg/d EGb 761 or vehicle. Ischemia-reperfusion had no effect on the rate of unlabeled Pam incorporation into brain phospholipids from palmitoyl-CoA; this rate also was unaffected by EGb 761. In contrast, ischemia-reperfusion increased the rate of incorporation of unlabeled AA from brain arachidonoyl-CoA by a factor of 2.3-3.3 compared with the control rate; this factor was further augmented to 3.6-5.0 by pretreatment with EGb 761. There is selective reincorporation of AA compared with Pam into brain phospholipids following ischemia. EGb 761 further accelerates AA reincorporation, potentially reducing neurotoxic effects of prolonged exposure of brain to high concentrations of AA and its metabolites.

The Fatty Acid method was used to determine whether incorporation of plasma radiolabeled arachidonic acid into brain phospholipids is controlled by phospholipase A2. Awake rats received an i.v. injection of a phospholipase A2 inhibitor, manoalide (10 mg/kg), and then were infused i.v. with [1-(14)C]arachidonate or [3H]arachidonate. Animals were killed after infusion by microwave irradiation, and tracer distribution was analyzed in brain phospholipid, neutral lipid and acyl-CoA pools. Calcium-independent phospholipase A2 activity in brain homogenate was reduced by manoalide, whereas phospholipase C activity was unaffected. At 60 min but not at 20 or 40 min after its injection, manoalide had significantly decreased by 50% incorporation of unesterified arachidonate into and turnover within brain phospholipids, taking into account dilution of the brain arachidonoyl-CoA pool by recycled arachidonate. Manoalide also increased by 100% the net rate of unesterified arachidonate incorporation into brain triacylglycerol. This study indicates that manoalide can be used to inhibit brain phospholipase A2 in vivo, and that phospholipase A2 plays a critical role in arachidonate turnover in brain phospholipids and neutral lipids.

We examined the effect of a clinically therapeutic dose of methyl 2-tetradecylglycidate (McN-3716, methyl palmoxirate, MEP) (2.5 mg/kg), an inhibitor of beta-oxidation of fatty acids, on incorporation of radiolabeled palmitic acid ([U-14C]PAM) from plasma into brain lipids of awake rats. Four hour pretreatment with 2.5 mg/kg MEP significantly increased the incorporation of [U-14C]PAM into brain lipids and substantially decreased aqueous radiolabeled metabolites in brain that can constitute unwanted background signal when analyzed by quantitative autoradiography. MEP treatment increased the lipid to aqueous background radioactivity from 0.8 to 3.0. Net rate of incorporation, k*, was significantly increased (60%) by MEP and was attributed to incorporation of [U-14C]PAM into phospholipid and triglyceride brain compartments. MEP treatment did not affect the size of the fatty acyl-CoA pool or the distribution of the various molecular acyl-CoA species. These results indicate that MEP, at a dose of 2.5 mg/kg (per os), can be used to increase incorporation of [1-(11C)]PAM for studying brain lipid metabolism in humans by positron emission tomography (PET).

The effects of anoxia and reoxygenation on major antioxidant enzyme activities were investigated in vitro in immortalized rat brain endothelial cells (RBE4 cells). A sublethal anoxic period of 12 h was assessed for RBE4 cells using the neutral red uptake test. Anoxia markedly influenced the specific activity of catalase and superoxide dismutase, with no major effect on glutathione peroxidase or glutathione reductase. After 24 h postanoxia, the superoxide dismutase activity modulated by the presence or absence of oxygen returned to control value. Damage and recovery of RBE4 immortalized rat brain endothelial cells in culture after exposure to free radicals and other oxygen-derived species provides a useful in vitro model to study anoxia-reoxygenation trauma at the cellular level.

In less than 10 years after the implementation of the World Anti-Doping Code and of the International Standard for Laboratories and its related Technical Documents, the analysis of human samples for the purpose of anti-doping testing has undergone a noticeable evolution. The research programs developed by the anti-doping organizations, and in particular the World Anti-Doping Agency (WADA), have created an unprecedented momentum in anti-doping science to strengthen the existing analytical methods, as well as to support the development and implementation of new and more sophisticated methodologies by the WADA-accredited laboratories. The integration of technical novelties into the analytical menus has been stimulated by the never-ending challenges posed by the adoption of more complex doping regimens by some athletes and their entourage. This increased sophistication of doping practices has also been reflected in the addition of new doping substances or methods on the WADA Prohibited Substances and Methods List. The integration of new anti-doping scientific paradigms with the development of the Athlete Biological Passport or the foreseen implementation of genomic- and proteomic-based tests constantly reshapes the environment of anti-doping analysis. This article provides a multiangle perspective on some of the key analytical challenges that anti-doping analytical science will face in 2012 and beyond.

The List of Prohibited Substances and Methods (the List), an International Standard published yearly by the World Anti-Doping Agency (WADA), determines which substances and methods are prohibited in sport in- and out-of-competition. Stimulants are included within drug class S.6 under the in-competition testing section of the List. Athletes may be tempted to use stimulants as ergogenic aids in-competition in order to temporarily improve their mental and/or physical functions by increasing alertness, aggressiveness, motivation, locomotion, heart rate, and reducing fatigue. The Prohibited List Expert Group, responsible for the maintenance of the List, approved WADA funding for a two-year study to determine whether athletes were also using stimulants to benefit from their performance-enhancing effects during the training phase between competitions (i.e., out-of-competition). This study, involving 11 WADA-accredited laboratories, found that the use of stimulants by athletes during training was not significantly prevalent (0.36% of positive findings), suggesting that this issue does not, at the moment, pose a further challenge to the fight against doping in sport. In addition, the study supports the current structure in the Prohibited List that differentiates banned substances into the in- and out-of-competition classifications.

Since 2004, when the World Anti-Doping Agency assumed the responsibility for establishing and maintaining the list of prohibited substances and methods in sport (i.e. the Prohibited List), cannabinoids have been prohibited in all sports during competition. The basis for this prohibition can be found in the World Anti-Doping Code, which defines the three criteria used to consider banning a substance. In this context, we discuss the potential of cannabis to enhance sports performance, the risk it poses to the athlete's health and its violation of the spirit of sport. Although these compounds are prohibited in-competition only, we explain why the pharmacokinetics of their main psychoactive compound, Δ(9)-tetrahydrocannabinol, may complicate the results management of adverse analytical findings. Passive inhalation does not appear to be a plausible explanation for a positive test. Although the prohibition of cannabinoids in sports is one of the most controversial issues in anti-doping, in this review we stress the reasons behind this prohibition, with strong emphasis on the evolving knowledge of cannabinoid pharmacology.

Most substances used for doping in sport are legitimate pharmaceutical products deviated from their intended therapeutic applications. One of the major challenges for anti-doping authorities, in anticipation of future doping trends, is to assess the doping potential of drugs in development by the health industry and to timely develop anti-doping analytical methods to detect their abuse before such drugs become available to athletes intending to use them as doping agents. In this regard, the World Anti-Doping Agency (WADA) has recently consolidated several agreements with representatives from the pharmaceutical sector in order to establish a framework of collaboration and to facilitate the identification and transfer of information on drugs in development. The context of the collaborative effort between WADA and the pharmaceutical and biotechnology industries, as well as the role of drug regulatory agencies in an integrated process in support of the fight against doping in sport are described in this article.

Due to its stimulatory effects on the central nervous system, and its structural similarity to banned stimulants such as ephedrine and methamphetamine, pseudoephedrine (PSE) at high doses is considered as an ergogenic aid for boosting athletic performance. However, the status of PSE in the International Standard of the Prohibited List as established under the World Anti-Doping Code has changed over the years, being prohibited until 2003 at a urinary cut-off value of 25 µg/ml, and then subsequently removed from the Prohibited List during the period 2004-2009. The re-consideration of this position by the World Anti-Doping Agency (WADA) List Expert Group has led to the reintroduction of PSE in the Prohibited List in 2010. In this manuscript, we present the results of two WADA-sponsored clinical studies on the urinary excretion of PSE and its metabolite cathine (CATH) following the oral administration of different PSE formulations to healthy individuals at therapeutic regimes. On this basis, the current analytical urinary threshold for the detection of PSE as a doping agent in sport has been conservatively established at 150 µg/ml

Since ancient times, unethical athletes have attempted to gain an unfair competitive advantage through the use of doping substances. A list of doping substances and methods banned in sports is published yearly by the World Anti-Doping Agency (WADA). A substance or method might be included in the List if it fulfills at least two of the following criteria: enhances sports performance; represents a risk to the athlete's health; or violates the spirit of sports. This list, constantly updated to reflect new developments in the pharmaceutical industry as well as doping trends, enumerates the drug types and methods prohibited in and out of competition. Among the substances included are steroidal and peptide hormones and their modulators, stimulants, glucocorticosteroids, beta2-agonists, diuretics and masking agents, narcotics, and cannabinoids. Blood doping, tampering, infusions, and gene doping are examples of prohibited methods indicated on the List. From all these, hormones constitute by far the highest number of adverse analytical findings reported by antidoping laboratories. Although to date most are due to anabolic steroids, the advent of molecular biology techniques has made recombinant peptide hormones readily available. These substances are gradually changing the landscape of doping trends. Peptide hormones like erythropoietin (EPO), human growth hormone (hGH), insulin, and insulin-like growth factor I (IGF-I) are presumed to be widely abused for performance enhancement. Furthermore, as there is a paucity of techniques suitable for their detection, peptide hormones are all the more attractive to dishonest athletes. This article will overview the use of hormones as doping substances in sports, focusing mainly on peptide hormones as they represent a pressing challenge to the current fight against doping. Hormones and hormones modulators being developed by the pharmaceutical industry, which could emerge as new doping substances, are also discussed.

We humans have long sought to enhance ourselves beyond normal through cosmetic surgery and drugs. Science is increasingly becoming humanity's partner and handmaiden in those efforts ( 1 ) and has added genetic manipulation to our enhancement tool kit. Many forms of human enhancement are becoming more feasible, sought-after, and even justifiable in the quest for healthier, happier, and longer lives.

Awake gerbils were subjected to 5 min of forebrain ischemia by clamping the carotid arteries for 5 min and then allowing recirculation. Radiolabeled arachidonic or palmitic acid was infused intravenously for 5 min at the start of recirculation, after which the brains were prepared for quantitative autoradiography or chemical analysis. Dilution of specific activity of the acyl-CoA pool was independently determined for these fatty acids in control gerbils and following 5 min of ischemia and 5 min of reperfusion. Using a quantitative method for measuring regional in vivo fatty acid incorporation into and turnover within brain phospholipids and determining unlabeled concentrations of acyl-CoAs following recirculation, it was shown that reperfusion after 5 min of ischemia was accompanied by a threefold increase compared with the control in the rate of reincorporation of unlabeled arachidonate that had been released during ischemia, whereas reincorporation of released palmitate was not different from the control. Selective and accelerated reincorporation of arachidonate into brain phospholipids shortly after ischemia may ameliorate specific deleterious effects of arachidonate and its metabolites on brain membranes.

Transient global cerebral ischemia affects phospholipid metabolism and features a considerable increase in unesterified fatty acids. Reincorporation of free fatty acids into membrane phospholipids during reperfusion following transient ischemia depends on conversion of fatty acids to acyl-CoAs via acyl-CoA synthetases and incorporation of the acyl group into lysophospholipids. To study the effect of ischemia-reperfusion on brain fatty acid and acyl-CoA pools, the common carotid arteries were tied for 5 min in awake gerbils, after which the ligatures were released for 5 min and the animals were killed by microwave irradiation. Twenty percent of these animals (two of 10) were excluded from the ischemia-reperfusion group when it was demonstrated statistically that brain unesterified arachidonic acid concentration was not elevated beyond the range of the control group. Brain unesterified fatty acid concentration was increased 4.4-fold in the ischemic-reperfused animals, with stearic acid and arachidonic acid increasing the most among the saturated and polyunsaturated fatty acids, respectively. The total acyl-CoA concentration remained unaffected, indicating that reacylation of membrane lysophospholipids is maintained during recovery. However, there was a substantial increase in the stearoyl- and arachidonoyl-CoA and a marked decrease in palmitoyl- and docosahexaenoyl-CoA. These results suggest that unesterified fatty acid reacylation into phospholipids is reprioritized according to the redistribution in concentration of acyl-CoA molecular species, with incorporation of stearic acid and especially arachidonic acid being favored.

Metals serve critical roles in brain as essential cofactors, catalysts, second messengers, and modulators of gene, enzyme, and receptor activity. Currently, eight metals, including calcium, magnesium, iron, copper, zinc, manganese, cobalt, and molybdenum, are known to be required for the normal development and function of the brian (Prohaska, 1987). Each must be supplied at specific levels to avoid signs of deficiency or toxic excess. Others, such as lead, aluminum, and mercury, are not essential, but are toxic if allowed to accumulate in the nervous system. Several metals, including iron, stimulate free radical formation and have been linked to oxidative damage in neurological disorders, including ischemia, stroke, and Parkinson’s disease (Riederer et al., 1989; Dexter et al., 1989; Griffiths and Crossman, 1993).

In vivo rates of incorporation and turnover of palmitate and arachidonate in brain phospholipids were measured in awake rats treated chronically with lithium, following intravenous infusion of radiolabeled palmitate and arachidonate, respectively. Chronic lithium, at a brain level considered to be therapeutic in humans, decreased turnover of arachidonate within brain phosphatidylinositol, phosphatidylcholine and phosphatidylethanolamine by up to 80% (P < 0.001). In contrast, lithium had a minimal effect on turnover of palmitate, causing only a 26% reduction in turnover in phosphatidylcholine (P < 0.01). These results suggest that a major therapeutic effect of lithium is to reduce turnover specifically of arachidonate, possibly by inhibiting phospholipase A2 involved in signal transduction. The effect may be secondary to the known action of lithium on the phosphoinositide cycle, by inhibiting the activity of inositol monophosphatase.

Early restriction of nutrients during the perinatal period of life can modify the development of the mammalian fetus and have marked repercussions on the ontogeny of the CNS. The brain is vulnerable to undernutrition, with delayed morphologic and biochemical maturation leading to impaired functions. The aim of the present investigation was to assess whether modified brain neurotransmitter and amino acid concentrations found in an animal model of intrauterine growth retardation were related to modified blood-brain amino acid transport properties. Four amino acids were tested: alanine and taurine, plus two neurotransmitter precursors, tryptophan and tyrosine. Intrauterine growth retardation was induced by restriction of maternal-fetal blood flow from the 17th d of gestation. Blood-brain transport of these amino acids was measured by i.v. injection of radiolabeled amino acids in 7-d-old, 21-d-old, and 60-d-old intrauterine growth-retarded or control rats. No major statistical differences were revealed either for brain regional transport or between intrauterine growth-retarded animals and controls at any age studied. Transfer coefficients and influxes remained statistically similar for almost all brain regions in both groups. A significant decrease and different time course for amino acid transport with age related to the blood-brain barrier maturation are confirmed in this model. Our results are related to a major role of the blood-brain barrier as a part of mechanisms leading to "brain growth sparing."

54Mn2+ uptake into brain and choroid plexus from the circulation was studied using the in situ rat brain perfusion technique. Initial uptake from blood was linear with time (30 s to 6 min) and extrapolated to zero with an average transfer coefficient of approximately 6 x 10(-5) ml/s/g for brain and approximately 7 x 10(-3) ml/s/g for choroid plexus. Influx from physiologic saline was three- to fourfold more rapid and exceeded that predicted for passive diffusion by more than one order of magnitude. The lower uptake rate from blood could be explained by plasma protein binding as the free fraction of 54Mn2+ in rat plasma was < or = 30%. Purified albumin, transferrin, and alpha 2-macroglobulin were each found to bind 54Mn2+ significantly and to restrict brain 54Mn2+ influx. The results demonstrate that 54Mn2+ is readily taken up into the CNS, most likely as the free ion, and that transport is critically affected by plasma protein binding. The results support the hypothesis that Mn2+ transport across the blood-brain barrier is facilitated by either an active or a passive mechanism.

Undernutrition during perinatal life, caused by restriction of blood supply to the fetus by ligating the uterine vessels produces intra-uterine growth retardation (IUGR) (8) and has a critical influence on brain function and development. In this case, it has been reported that vascular concentrations of some amino acids were modified several days after undernutrition trauma occurred (6) and that modifications in cerebral monoamine or amino acid concentrations were observed in several brain regions (1,2). To further investigate the origin of the brain alterations, we examined the possible role of the blood-brain barrier at the interface between the two modified compartments.