Roles of Gonadal Steroids on Exocrine Secretion of Isolated Perfused Rat Pancreas

To clarify the roles of gonadal steroids on pancreatic exocrine secretion, effects of progesterone and estradiol-$17{\beta}$ on spontaneous and secretagogue-induced exocrine response of isolated perfused rat pancreas were investigated. Intra-arterial infusion of progesterone resulted in significant increase of the spontaneous pancreatic fluid and amylase secretion dose-dependently. However, estradiol-$17{\beta}$ did not exert any influence on spontaneous pancreatic exocrine secretion. Exogenous secretin, cholecystokinin (CCK), and acetylcholine markedly stimulated pancreatic fluid and amylase secretion. Progesterone initially enhanced secretin-induced amylase secretion, but this stimulatory response declined thereafter to basal value. Moreover, secretin-induced fluid secretion was not affected by infusion of progesterone. Therefore, initial increase of secretion-induced amylase secretion by progesterone seems to be a non-specific action by washout effect of secretin. Estradiol-$17{\beta}$ failed to change the secretin-induced fluid and amylase secretion. Both progesterone and estradiol-$17{\beta}$ did not exert any influence on CCK-induced fluid and amylase secretion. Acetylcholine-induced exocrine secretion of isolated perfused pancreas also was not affected by intra-arterial infusion of progesterone or estradiol-$17{\beta}$. It is concluded from the above results that progesterone could enhance the spontaneous pancreatic fluid and amylase secretion of isolated perfused rat pancreas through non-genomic shortterm action, and that these effects could be masked by more potent stimulants such as secretin, CCK, and acetylcholine.