INTESTINAL MUCOSAL ORNITHINE DECARBOXYLASE AND BRUSH-BORDER MEMBRANE VESICLE NA-H+ EXCHANGE ACTIVITIES IN DIABETIC RATS()

To determine the possibility that intestinal mucosal ornithine decarbo xylase activity can modulate mucosal brush border membrane Na+-H+ exch ange activity, we studied the relationship between jejunal mucosal orn ithine decarboxylase activity and mucosal brush border membrane Na+-H exchange activity in adolescent streptozotocin-diabetic and normal co ntrol rats. Diabetes was associated with enhanced intestinal mucosal o rnithine decarboxylase and Na+-H+ exchange activities. Groups of diabe tic and control rats were given difluoromethylornithine in drinking wa ter to suppress intestinal mucosal ornithine decarboxylase activity. A s expected, 10 days after induction of diabetes, intestinal mucosal we ight (67.7 mg/cm vs 56.1 mg/cm), DNA (47.3 mu g/mg protein vs 32.7 mu g/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 Na-22(+) uptake (32.5 nmol/mg protein/15 min vs 15.2 nmol/mg protein/15 min), were significantly greater in diabetic t han in control rats. Treating diabetic and control rats with difluorom ethylornithine suppressed jejunal mucosal growth by over 30%, ornithin e decarboxylase activity by over 80%, and brush border membrane vesicl e Na-22(+) uptake by over 60%. Highly significant direct correlations (r > 0.900) were observed between jejunal DNA content, mucosal ornithi ne decarboxylase activity, and brush border membrane vesicle Na+-H+ ex change activity. The above findings suggest that jejunal mucosal ornit hine decarboxylase activity can modulate mucosal epithelial proliferat ion and mucosal brush border membrane Na+-H+ exchange activity.