Intestinal Mucosal Ornithine Decarboxylase and Brush Border Membrane Vesicle Na + -H + Exchange Activities in Diabetic Rats

Abstract

To determine the possibility that intestinal mucosal ornithine decarboxylase activity can modulate mucosal brush border membrane Na⁺-H⁺ exchange activity, we studied the relationship between jejunal mucosal ornithine decarboxylase activity and mucosal brush border membrane Na⁺-H⁺ exchange activity in adolescent streptozotocin-diabetic and normal control rats. Diabetes was associated with enhanced intestinal mucosal ornithine decarboxylase and Na⁺-H⁺ exchange activities. Groups of diabetic and control rats were given difluoromethylornithine in drinking water to suppress intestinal mucosal ornithine decarboxylase activity. As expected, 10 days after induction of diabetes, intestinal mucosal weight (67.7 mg/cm vs 56.1 mg/cm), DNA (47.3 M9/mg protein vs 32.7 Mg/mg protein), ornithine decarboxylase activity (1107 units/hr vs 654 units/hr), and brush border membrane vesicle Na⁺-H⁺ exchange activity, assessed as V_max of ²²Na+ uptake (32.5 nmol/mg protein/15 min vs 15.2 nmol/mg protein/15 min), were significantly greater in diabetic than in control rats. Treating diabetic and control rats with difluoromethylornithine suppressed jejunal mucosal growth by over 30%, ornithine decarboxylase activity by over 80%, and brush border membrane vesicle ²²Na+ uptake by over 60%. Highly significant direct correlations (r > 0.900) were observed between jejunal DNA content, mucosal ornithine decarboxylase activity, and brush border membrane vesicle Na⁺-H⁺ exchange activity. The above findings suggest that jejunal mucosal ornithine decarboxylase activity can modulate mucosal epithelial proliferation and mucosal brush border membrane Na⁺-H⁺ exchange activity.