Differential activation of adenylate cyclase by secretin and VIP receptors in the calf pancreas.

Results:We successfully amplified, by reverse transcriptase-polymerase chain reaction, a fragment of the SEC-R gene from 119-day-old calf pancreas. This sequence shows higher homology with SEC-R than with vasoactive intestinal polypeptide (VIP)-1 and VIP-2 receptors from other species. Northern blot analysis detected a 1.8-kb transcript. Accordingly, secretin stimulates AC activity in calf pancreatic membranes isolated from 28and 119-day-old animals with a potency (Ka) of 1.9 to 2.7 nmol/L. Maximal AC stimulation induced by secretin represented a 3to 4-fold increase of basal activity. AC activation by secretin was inhibited by the 2 SEC-R antagonists, [c4,5] secretin (l mmol/L) and [5-27] secretin (10 mmol/L). Interestingly, [c4,5] secretin was ineffective against VIP-induced AC stimulation.