Arginine vasopressin inhibits fluid secretion in guinea pig pancreatic duct cells

The effects of arginine vasopressin (AVP) on pancreatic ductal secretion were studied in guinea pigs. In the isolated vascularly perfused pancreas, AVP reduced secretin-stimulated fluid secretion and increased the vascular resistance when the perfusion rate was held constant. In the isolated interlobular duct segments, AVP inhibited secretinstimulated fluid secretion, indicating the direct inhibitory action of AVP on the duct cells. AVP affected neither the basal nor the secretin-induced cAMP productions, suggesting that AVP inhibits the fluid secretion at a point distal to the production of cAMP. AVP increased intracellular Ca2+ concentration ([Ca2+](i)) in the absence of extracellular Ca2+. When [Ca2+](i) was elevated by the application of thapsigargin, AVP caused a rapid decrease in [Ca2+](i). AVP seems to activate both Ca2+ release from intracellular stores and Ca2+ efflux across the plasma membrane, but its relation to the inhibition of fluid secretion remains to be clarified. It is concluded that AVP directly inhibits secretin-stimulated ductal fluid secretion; the guinea pig pancreas.