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To determine the effects of age, feeding regimen, and antenatal glucocorticoids on intestinal permeability, preterm infants (n = 132) were stratified by gestational age and by diet (mothers' own milk versus preterm formula), and assigned randomly to one of four feeding regimens: early-continuous, early-bolus, standard-continuous, and standard-bolus. At 10, 28, and 50 d of age permeability was determined by measuring the ratio of lactulose/ mannitol in the urine after the two sugars were administered enterally for 30 h. The mean (+/-SE) birth weight and gestational age of the infants were 1044 +/- 13 g and 27 +/- 0.1 wk, respectively. Permeability changed as a function of age (p = 0.003). Early feeding was associated with a reduction in permeability at 10 d of age (p = 0.01). Antenatal steroid administration was associated with decreased permeability at 28 d of age (p = 0.017). The feeding of human milk (versus formula) was associated with decreased permeability at 28 d of age (p = 0.02). Continuous versus bolus feeding did not affect permeability.

Premature infants are susceptible to disease related to deficient dietary calcium intake. Studies in adults suggest carbohydrates can enhance calcium absorption. However, little is known about how carbohydrates affect calcium absorption in premature infants due to a lack of direct in vivo studies. We adapted the triple lumen perfusion method for use in premature infants to compare calcium absorption 36 mmol/L (1.44 g/L) in the absence and presence of either 70 g/L lactose or glucose polymers. 44Ca was added to determine endogenous calcium losses. Fourteen infants were studied (gestational age: 31 +/- 0.4 wk; study weight: 1590 +/- 105 g; mean +/- SEM). Calcium absorption from the glucose polymer solution was greater than that from the control and lactose solutions (0.17 +/- 0.05 mumol.min-1.cm-1 versus 0.04 +/- 0.04 and 0.008 +/- 0.045 mumol.min-1.cm-1, respectively). Calcium absorption correlated positively with water and carbohydrate absorption. The rate of carbohydrate absorption was greater from the glucose polymers than from the lactose solution (0.40 +/- 0.10 mg.min-1.cm-1 versus 0.22 +/- 0.06, respectively). Based upon 44Ca absorption, endogenous calcium loss appeared to account for less than 1% of total calcium flux. We conclude that glucose polymers, but not lactose, enhance calcium absorption in the premature infant, a fact that may be useful in formula design.

Factors, such as insulin, found in human and pig colostrum and mature milk likely influence small intestinal growth and development. Although pharmacologic doses of insulin injected parenterally may accelerate small intestinal development in altricial animals such as the rodent, the effects of oral insulin on intestinal development have not been studied. In the first of two studies, we randomized 2-d-old miniature piglets to receive bottle-feedings of a swine weaning milk formula with (group F + I) or without (group F) the addition of insulin. Serum glucose, insulin, and cortisol were measured before and 1 h after the first feeding the piglets received at our facility. In the second study, piglets were randomized (groups F and F + I) and fed for 6 d, after which blood samples were obtained as in the first experiment. The piglets were then killed and the small intestine removed for analysis. We found no differences between groups in serum glucose, insulin, and cortisol at both 2 and 8 d of age, both before and after feeding. In the second experiment, small intestinal weight was greater in the F + I than in the F group. Although no differences were noted between groups in the jejunum, values were greater for group F + I versus group F for ileal mucosal weight, protein, RNA, lactase, and maltase activities. No differences were found between groups in ileal DNA or sucrase activity. We conclude that the administration of oral insulin stimulated an increase in ileal mass and disaccharidase activity in the newborn miniature pig without apparent concomitant changes in serum glucose, insulin, or cortisol.

Unlabelled: The aminopyrine breath test has been used in adults as a measure of hepatic N-demethylase activity. In order to study maturational changes in enzyme function, 13C aminopyrine (2 mg/kg) was administered orally to infants (n = 16) between the ages of 1 and 38 wk. Breath samples were collected for 6 h after administration of the labeled aminopyrine for the measurement of 13CO2 enrichment. Using a number of different scoring methods to quantitate 13CO2 elimination of breath, demethylation of aminopyrine was found to be positively correlated to age. By 20 wk of age, some infants had rates of elimination similar to those measured in adults. Absorption was excluded as a limiting variable, because no improvement in oxidation rates was found when the aminopyrine was readministered as an intravenous bolus. Changes in nutritional status and route of feeding (enteral versus parenteral) did not prevent the effect of maturation on aminopyrine elimination., Conclusions: 1) maturational differences are seen in the metabolism of aminopyrine; 2) these differences may reflect immaturity of N-demethylase activity or diversion of the liberated formaldehyde into biosynthetic rather than oxidative pathways.

Because mucosal glucoamylase is most active against glucose polymers less than 10 glucose units in length, longer chain polymers may not be completely absorbed by young infants. In order to investigate this possibility, the absorption and oxidation of 13C-rich glucose, short-chain (3 to 8 glucose units in length) and long-chain (average length 43 units) glucose polymers (GP) were compared in 12 healthy, 1-month-old infants. Recovery of the GP and glucose in stool was measured by determining the 13C enrichment of stool. The oxidation of the GP was measured by tracing the increase in breath 13CO2 after GP were fed. Carbohydrate malabsorbed in the small bowel was assessed by measurement of breath H2, a gas formed from the fermentation of carbohydrate in the colon. Analysis of the infants' stools revealed that one infant excreted 9.7% of the dose of glucose, another 6.7% of the dose of short-chain GP, and five infants excreted 2.6 to 18.5% (mean 8.4%) of the dose of long-chain GP. The percent of the administered dose recovered in breath was similar among substrates (mean = 28.7% of the dose fed). A rise in breath H2 greater than 20 ppm was found in four of the 12 infants after the feeding of glucose, in five of 12 after the short-chain GP, and in six of 12 after the long-chain GP. None of the infants developed diarrhea. The results suggest that healthy young infants do not absorb long-chain GP as completely as they absorb short-chain GP.(ABSTRACT TRUNCATED AT 250 WORDS)