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Alterations in postnatal intestinal function during chronic hypoxemia
D Bernstein1, J G Bell, L Kwong
1Division of Cardiology, Stanford University, California 94305.
Insights
Chronic hypoxemia in newborn lambs reduced overall growth but did not affect small intestine size. Digestive enzyme activity, particularly lactase, was significantly decreased in hypoxemic lambs, impacting nutrient absorption.
Area of Science:
- Physiology
- Gastroenterology
- Pediatric Cardiology
Background:
- Chronic hypoxemia is a known cause of growth failure in infants with congenital heart disease.
- The impact of infantile hypoxemia on gastrointestinal development and function requires further investigation.
Purpose of the Study:
- To investigate the effects of chronic hypoxemia on small intestinal growth and digestive enzyme activity in newborn lambs.
- To determine if hypoxemia during infancy impairs gastrointestinal development.
Main Methods:
- Newborn lambs were subjected to chronic hypoxemia (aortic oxygen saturation 60-74%) for 2 weeks using a pulmonary artery occluder and atrial septostomy.
- Control lambs were age-matched.
- Small intestinal growth (weight, length, mucosal protein/DNA) and digestive enzyme activities (lactase, maltase, etc.) were analyzed.
Main Results:
- Hypoxemic lambs exhibited a significantly reduced somatic growth rate (60% of controls) without altered caloric intake.
- Small intestinal growth parameters (weight, length, mucosal content) were not significantly different between groups.
- Specific and total lactase activity in the small intestine were significantly decreased in hypoxemic lambs.
- Other digestive enzymes showed non-significant decreases in activity.
Conclusions:
- Chronic infantile hypoxemia impairs somatic growth but does not inhibit small intestinal growth in lambs.
- Reduced lactase activity in hypoxemic lambs suggests impaired carbohydrate digestion and potential malabsorption.
- These findings highlight the gastrointestinal consequences of hypoxemia in early development.
Abstract:
Growth failure is a major complication of chronic hypoxemia, as seen in infants and children with cyanotic congenital heart disease. To determine whether chronic hypoxemia during infancy affects the gastrointestinal tract, we examined small intestinal growth and digestive enzyme activities in chronically hypoxemic newborn lambs and in age-matched controls. Chronic hypoxemia was produced by placing an inflatable occluder around the main pulmonary artery and performing a balloon atrial septostomy. Aortic oxygen saturation was reduced to 60-74% for 2 wk, after which the small intestine was removed for analysis. During chronic hypoxemia, somatic growth rate was decreased to 60% of control (hypoxemic, 135 +/- 20 versus control, 216 +/- 26 g/d, p less than 0.02). No differences in caloric intake were found (hypoxemic, 129 +/- 4 versus control, 128 +/- 4 kcal/kg/d). Chronic hypoxemia did not alter small intestinal growth, as measured by jejuno-ileal weight, jejuno-ileal length, mucosal weight, or mucosal protein or DNA contents. However, sp act of lactase, the principal disaccharidase of the infant lamb intestine, were significantly decreased (hypoxemic, 0.08 +/- 0.01 versus control, 0.146 +/- 0.03 units of enzyme activity/mg DNA, p less than 0.05), as were the total small intestinal contents of lactase (hypoxemic, 61.7 +/- 7.0 versus control, 120.6 +/- 21.7 units of enzyme activity, p less than 0.01). There also were decreases in specific and total activities of other digestive enzymes such as maltase, amino-oligopeptidase, and alkaline phosphatase in hypoxemic intestine that did not achieve statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)