Actions of a new peptide from porcine intestine (PHI) on pancreatic secretion in the rat and turkey

A newly purified peptide from porcine intestine (PHI) was found to be a potent stimulant of the flow of pancreatic juice in anaesthetized turkeys (D₅₀ 75 ng/kg), and was about half as active as chicken vasoactive intestinal peptide (VIP, D₅₀ 47 ng/kg) to which it is structurally related. However, in anaesthetized rats, PHI, like VIP, was a weak stimulant of the flow of pancreatic juice. In contrast, porcine secretin, which is also structurally related to PHI, is a potent stimulant of the rat pancreas and a weak stimulant in birds. PHI had less than 0.01% immunochemical potency in a VIP radioimmunoassay. We conclude that PHI has VIP-like rather than secretin-like actions on the pancreas in birds and mammals; an avian counterpart of PHI could play a physiological role in the control of the exocrine pancreas.