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Duchenne and Becker muscular dystrophies (DMD and BMD) are associated with decreased total nitric oxide (NO). However, mechanisms leading to NO deficiency with consequent muscle-cell degeneration remain unknown. To address this issue, we examined skeletal muscles of DMD and BMD patients for co-expression of NO synthase (NOS) with nitrotyrosine and transcription factor CREB, as well as with enzymes engaged in NO signaling. Employing immunocytochemical labeling, Western blotting and RT-PCR, we found that, in contrast to the most commonly accepted view, neuronal NOS was not restricted to the sarcolemma and that muscles of DMD and BMD patients retained all three NOS isoforms with an up-regulation of the inducible NOS isoform, CREB and nitrotyrosine. We suggest that enhanced nitrotyrosine immunostaining in muscle fibers as well as in the vasculature of DMD and BMD specimens reflects massive oxidative stress, resulting in withdrawal of NO from its regular physiological course via the scavenging actions of superoxides.

Prostaglandin (PG) D(2) exerts pro-inflammatory and anti-inflammatory functions under various pathological conditions. We found that the immunoreactivity of hematopoietic PGD synthase (HPGDS) appeared in necrotic muscle fibers, mainly in foci of grouped necrosis, in Duchenne's muscular dystrophy (DMD) and polymyositis (PM), but not in Becker's muscular dystrophy or in Fukuyama-type congenital muscular dystrophy. The HPGDS expression in DMD and PM was observed to be transient in hyalinated fibers at the early necrotic stage but not detected in opaque fibers, in fibers infiltrated by monocytes/lymphocyte, or in regenerating fibers. The immunoreactivities of a cytosolic form of phospholipase A(2) and cyclooxygenase-2, the upstream enzymes of the arachnoid acid cascade, were similarly observed in the HPGDS-positive fibers, suggesting that PGD(2) was produced in situ in those necrotic muscle fibers.

A calcium-dependent proteinase (calpain) has been suggested to play an important role in muscle degradation in Duchenne muscular dystrophy (DMD). In immunohistochemical studies, calpain and its endogenous inhibitor (calpastatin) were located exclusively in the cytoplasm in normal human muscles. The intensity of the staining was stronger in type 1 than in type 2 fibers. Quantitative immunohistochemical study showed an increase of calpain in biopsied muscles from the patients with DMD and Becker muscular dystrophy. Abnormal increases in calpain and calpastatin were demonstrated mainly in atrophic fibers, whereas necrotic fibers showed moderate or weak immunoreactions for the enzymes. Opaque fibers and hypertrophic fibers were negative. Not all dystrophin-deficient muscle fibers necessarily showed a strong reaction for calpain. We suggest that calpain may play an important role in muscle fiber degradation, especially in the early stage of muscle degradation in muscular dystrophy.

Activity of creatine kinase isoenzyme MB in serum and variants of red cell acetylcholinesterase were determined in patients with Duchenne muscular dystrophy, in other forms of Dystrophy and in family members of Duchenne patients and healthy controls. Creatine kinase isoenzyme MB was observed only in all cases of DMD as well as variants of red cell acetylcholinesterase characterized by so-called inhibitor numbers. Carriers of Duchenne muscular dystrophy can be distinguished from Duchenne patients and healthy controls by estimation of Acetylcholinesterase variants.

In extracts derived from whole blood, a high molecular weight fraction of the diphenoloxidase enzymes has a significantly diminished specific activity in patients and definite carriers (heterozygotes) of the X-linked, recessive (Duchenne) form of muscular dystrophy. This anomaly was studied using spots of blood which had been collected on absorbent paper and stored at 4 degrees C for variable periods of time. Fractions enriched in the enzymes were obtained by subjecting aqueous extracts of the spots to treatment with an anion exchange resin (DEAE Sephadex A 50) followed by gel filtration on Sephadex G-25. It is of interest that this anomaly was observed in some definite carriers of the mutant gene who had on several occasions a serum creatine kinase level in the normal range. The significance of these observations is discussed.

A report by Bullock and coworkers has emphasized the need for standardization of the CK assay in carrier detection for DMD. A collaborative study, according to a well-specified design and involving two laboratories in Paris and Lyon, indicates that the reliability of this assay can be improved provided that special attention is paid to information about participating subjects, laboratory protocol, and repeated sampling. On a random sample of young women, mean and variance of ln(CK) are 1.66 and 0.015 respectively. Within and between variance components are in a 3:4 ratio, homogeneous between populations. Additional use of a common test serum should insure good reliability of this assay among laboratories.

Lipid peroxidation (LP) and superoxide dismutase (SOD) activity were determined in erythrocytes and skeletal muscle obtained from patients with limb-girdle and facioscapulohumeral muscular dystrophies, neurogenic atrophies and from age-matched control subjects. Neither lipid peroxidation nor SOD activity in erythrocytes of patients differed from control values. SOD activity and LP in muscle specimens were also normal in types of neurogenic atrophy. Lipid peroxidation in the muscle from patients with adult types of muscular dystrophy had a tendency to be increased. The values were widely scattered, the highest being obtained in the older patients with long duration of disease.

In a previous article (Demos et al. 1981), we reported a significant and specific reduction of the activity index (AI) of the diphenoloxidases (DPox) in patients and heterozygotes with progressive Duchenne muscular dystrophy (DMD), which is transmitted genetically by female subjects by a sex-linked recessive mechanism (SLR). This same anomaly was detected in patients suffering from other types of dystrophy: Becker, limbgirdle, fascio-scapulo-humeral, and in heterozygotes of either sex in diseases transmitted by an obviously recessive autosomic mechanism. These anomalies were detected using blood spots collected on absorbent paper and stored at 4 degrees C for different periods. They were of the same type as had previously been detected using blood platelets (Demos 1973).

Adenylate kinases, small organ-specific isoenzymes which appear after tissue damage in the blood plasma are partly eliminated via the kidney. After intravenous administration of 3000 enzyme units of 14C-labelled adenylate kinase to rats, about 50% of the enzyme and of the radioactivity are found in the urine within 7 minutes. The elimination of adenylate kinase from the serum occurs in two phases, a faster (half-life 16 minutes) and a slower (half-life 160 minutes). After intravenous adminstration of adenylate kinase to humans, a part of the activity was recovered in the urine within minutes. The potential use of assaying adenylate kinase levels for early diagnosis of myocardial infarction is discussed. Using various skeletal muscle diseases as examples, the possible use of the very rapid elimination of adenylate kinase from the serum in monitoring the course of the acute illnesses is described. The competitive inhibitor diadenosine pentaphosphate (AP5A) has a much higher affinity for the adenylate kinases from erythrocytes, heart or skeletal muscle than for the isoenzymes from liver or kidney. Therefore, AP5A can be used for the differential determination of adenylate kinase isoenzymes in the blood plasma or the urine.