Relation between pancreatic growth and blood flow

Islet hyperperfusion during prediabetic phase in OLETF rats, a model of type 2 diabetes

Although it has been hypothesized that initial hyperperfusion followed by late hypoperfusion in islet circulation occurs in rodent models of type 2 diabetes, islet blood flow has not been measured during prediabetic phase. We studied islet blood flow in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of slowly progressive obese type 2 diabetes. Islet blood flow was measured by the two-color microsphere method under anesthesia at different ages. Islet blood flow was significantly higher in young OLETF rats compared with control Long-Evans Tokushima Otsuka (LETO) rats when the former were not obese or diabetic and had normal insulin secretion at 5 weeks of age (LETO 4.6 +/- 1.1, OLETF 8.8 +/- 1.2 ml. min(-1). mg(- 1), P < 0.01). At 6 months of age, islet hyperperfusion was observed in OLETF rats, and >40% of whole pancreatic blood flow was diverted into islets in OLETF rats. Prevention of obesity by food restriction increased basal islet blood flow. On the other hand, long-term hyperglycemia induced by sucrose feeding decreased fractional islet blood flow as well as glucose-stimulated islet blood flow. Our results indicate that hyperperfusion is present during the preobese and prediabetic phase in our type 2 diabetes rats.

Dissociation of CCK-8-induced fluid secretion from protein secretion by ion-transport blockers in rat pancreas

The effects of ion-transport blockers on CCK-8-induced protein output and concomitant fluid secretion were compared in isolated, perfused normal and hypertrophied rat pancreata. In the normal pancreas, perfusion with ouabain (1 mM), amiloride (1 mM), furosemide (1 mM), or SITS (0.1 mM) caused corresponding inhibition of both fluid and protein secretion that was induced by 100 pM CCK-8. Hypertrophy of the pancreas was produced by oral administration of a synthetic protease inhibitor (FOY-305) once a day for 3 wk. In the hypertrophied pancreas, perfusion with ouabain (0.1 or 1 mM) or amiloride (0.1 mM or 1 mM) decreased CCK-8-induced fluid secretion without changing CCK-8-induced protein output. Perfusion with furosemide (1 mM) inhibited both fluid and protein secretion induced by CCK-8, but the amount of inhibition of fluid secretion was much greater than that of protein secretion. Perfusion with SITS (0.1 mM) significantly decreased CCK-8-induced fluid secretion but not protein secretion. These results indicate that in contrast to a normal rat pancreas, the coupling of fluid and protein secretion induced by CCK-8 can be disrupted by experimental procedures that induce hypertrophy in the rat pancreas.