Vasoactive intestinal peptide: a secretin-like partial agonist for pancreatic secretion in man.

The responses of pancreatic volume flow and bicarbonate output to intravenous vasoactive intestinal peptide (VIP, 0.8 to 3.2 microgram per kg per hr) and synthetic secretin (32.2 to 129 ng per kg per hr) were compared intraindividually in 5 healthy volunteers. Pure pancreatic juice was obtained by endoscopic cannulation of the main pancreatic duct. The mean +/- SEM observed maximal response of secretin-stimulated juice flow was 248 +/- 7 microliter per kg per 5 min, whereas the observed maximal response for VIP-evoked juice flow was 48 +/- 6 microliter per kg per 5 min. The observed maximal secretin-induced bicarbonate output was 30 +/- 2 muEq per kg per 5 min, and the maximal VIP-related response was 4.3 +/- 0.9 muEq per kg per 5 min. In addition to low efficacy, high dose requirements, and side effects (significant rise in pulse rate and cutaneous flushing at 3.2 micrograms per kg per hr) argue against a major physiological role of VIP as a hormonal stimulant of human pancreatic bicarbonate secretion.