Highly purified secretin, infused endoportally in five conscious mongrel dogs at a rate of 10 clinical units per min for 20 min, caused a prompt and statistically significant reduction in the pancreaticoduodenal vein level of pancreatic glucagon from a control average of 1130 pg/ml (SEM±312) to a nadir of 492 pg/ml (SEM±194) 15 min later (P < 0.01). During modest hyperglycemia of about 130 mg/100 ml, induced by glucose infusion, the infusion of secretin at the same rate elicited even more dramatic suppression of pancreaticoduodenal glucagon levels to virtually unmeasurable concentrations. At a lower rate of infusion (5 U priming injection followed by 1 U/min for 20 min) significant suppression of glucagon secretion during hyperglycemia was also observed. Stimulation of endogenous secretin release by the intraduodenal administration of 14 mEq of HCl in 10 dogs during intravenous glucose infusion was followed by a decline in pancreaticoduodenal vein glucagon from 130 pg/ml (SEM±34) to a nadir of 99 pg/ml (SEM±32) 5 min later (P < 0.05).
Fausto Santeusanio, Gerald R. Faloona, Roger H. Unger