Abstract
In anaesthetized rats, a dose-dependent effect of different intraduodenal HCI loads (0.6, 1.2, 6 and 12 mmol/h) on exocrine pancreatic secretion and plasma levels of secretin and VIP has been observed. The flow rate of pancreatic juice showed a significant increase at all the doses used; the integrated percentage response (IPR) of flow were 359%, 595%, 894% and 1371% for, respectively, 0.6, 1.2, 6 and 12 mmol/h. The increase of protein output only achieved statistical significance at HCI 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. Portal levels of secretin and VIP were measured by specific radioimmunoassays. Significant increase of secretin concentration was observed at HCI loads of 1.2 mmol/h or more, whilst VIP levels only increased significantly 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% and 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 stimulating exocrine pancreatic secretion in response to intraduodenal loads of acid in this species.