DOSE-RESPONSE EFFECT OF INTRADUODENAL HCL ON EXOCRINE PANCREATIC-SECRETION, PORTAL SECRETIN, AND VIP PLASMA-LEVELS IN ANESTHETIZED RATS

In anaesthetized rats, a dose-dependent effect of different intraduode nal HCI loads (0.6, 1.2, 6 and 12 mmol/h) on exocrine pancreatic secre tion and plasma levels of secretin and VIP has been observed. The flow rate of pancreatic juice showed a significant increase at all the dos es used; the integrated percentage response (IPR) of flow were 359%, 5 95%, 894% and 1371% for, respectively, 0.6, 1.2, 6 and 12 mmol/h. The increase of protein output only achieved statistical significance at H CI loads of 6 mmol/h or more; the IPR of protein output were 153%, 305 %, 320% and 420% for, respectively, 0.6, 1.2, 6 and 12 mmol/h HCI. Por tal levels of secretin and VIP were measured by specific radioimmunoas says. Significant increase of secretin concentration was observed at H CI loads of 1.2 mmol/h or more, whilst VIP levels only increased signi ficantly after intraduodenal HCI load of 6 mmol/h or more. The IPR of secretin release were 180%, 203%, 280% and 322% for, respectively, 0.6 , 1.2, 6 and 12 mmol/h HCI and IPR of VIP release were 3%, 20%, 244% a nd 315% for, respectively, 0.6, 1.2, 6 and 12 mmol/h HCI. Our results suggest that secretin may play a more prominent role than VIP in stimu lating exocrine pancreatic secretion in response to intraduodenal load s of acid in this species.