Effects of Hypoxia on the Development of Intestinal Enzymes in Neonatal and Juvenile Rats

Abstract

Hypoxia in the neonate is known to alter the activity of hepatic and pancreatic enzymes involved in lipid and carbohydrate metabolism. The purpose of this study was to evaluate the effect of neonatal hypoxia on the activity of intestinal enzymes, and to determine whether the administration of glucocorticoids to neonates can mimic the effects of hypoxia. Hypoxia in neonatal rats (0-7 days) increased protein content, and lactase and maltase activity in the duodenal and the jejunal segments of the small intestine compared with normoxic controls. Hypoxia in juvenile rats (28-35 days) did not change these enzymes. Two weeks after returning hypoxic (0-7 days) pups to normoxia, their body weight remained lower than the age-matched controls. In the group recovering from hypoxia, sucrase, maltase, and leucine aminopeptidase activities were lower in the duodenal and the jejunal segment. Compared with controls, LDH activity was lower only in the jejunal intestine in the group recovering from hypoxia. All enzyme activities returned to control levels 3 weeks after recovery. Neonatal rats treated with dexamethasone had a decrease in body weight, but increases in sucrase and maltase activity in both the duodenal and the jejunal segment. Hypoxia in newborn rats caused a delayed maturation of small intestinal enzymes. Increases in serum glucocorticoids after hypoxic exposure probably do not play a major role in the delayed maturation of the disaccharidase activity in the small intestine.

Epidermal Growth Factor and Parathyroid Hormone-related Peptide mRNA in the Mammary Gland and their Concentrations in Milk: Effects of Postpartum Hypoxia in Lactating Rats

“…Glucocorticoids and insulin shift the maturation of enzyme functional capacity towards that of the adult, including increased sucrase and decreased lactase activity [46]. We have previously shown that lactase and maltase activity was increased in the small intestine of hypoxic pups, while there were no changes in sucrase activity [35]. Therefore, the enzyme profiles did not correlate with changes in circulating hormone concentrations.…”

“…Stomach contents of hypoxic pups had increased concentrations of diacylglycerides and saturated (14:0 and 16:0) and polyunsaturated (18:3n-3 and 20:5n-3) fatty acids [15]. Chronic hypoxia also elicited changes in neonatal digestive function, including increased small intestinal lactase and maltase activity and decreased pancreatic lipase activity [35,39].…”

“…We hypothesized that exposure to chronic hypoxia causes significant changes in milk-derived peptide composition that are reflected in changes in gene expression. This adaptation may modulate neonatal small intestinal enzyme activity, which we have demonstrated previously [35]. Because we have also shown that hypoxia lowers maternal food intake [7], we studied normoxic dams that were fed ad libitum and normoxic dams that were pair fed to account for the effects of decreased caloric intake per se on milk composition.…”

Gastrointestinal Function

“…Neonatal hypoxia has been associated with delayed intestinal enzyme development in animal models [ 33 ] and the cat small intestine has been used as a model to examine intestinal lymphatic protein clearance, with a reduction in arterial oxygen tension from 108 to 35 mmHg having no effect [ 34 ].…”

Interrelationships between tissue iron status and erythropoiesis during postweaning development following neonatal iron deficiency in rats

“…These age-dependent changes in absorption have been attributed to the intrinsic characteristics of the intestine rather than bioavailability (12,14). Iron deficiency and hypoxia in neonatal rats is known to cause a delay in the maturation of intestinal enzymes (6,18). The precise regulation of physiologically active iron in the tissues combined with the developmental changes in neonates will be critical for later development and for preventing a risk of chronic diseases (8).…”