Effect of vasoactive intestinal peptide, peptide histidine isoleucine and growth hormone-releasing factor-40 on bombesin-like immunoreactivity, somatostatin and gastrin release from the perfused rat stomach

Bombesin-like immunoreactivity (BLI) has been demonstrated in neurons of the gastrointestinal tract and gastric BLI secretion can be demonstrated in response to the classical neurotransmitter acetylcholine. Since structurally related peptides VIP, PHI and GRF have to be considered as peptidergic neurotransmitters it was of interest to determine their effect on gastric BLI secretion. Additionally, somatostatin (SLI) and gastrin secretion was examined. The isolated stomach of overnight fasted rats was perfused with Krebs-Ringer buffer via the celiac artery and the effluent was collected via the portal vein. The gastric lumen was perfused with isotonic saline at pH7 or pH2. All four peptides were tested at a dose of 10(-11) M and 10(-8) M at both pH levels and in addition the effect of VIP and PHI was examined at 10(-14) M and 10(-12) M during luminal pH2. At luminal pH7 VIP and PHI stimulated SLI release at 10(-8) M but had no effect on BLI or gastrin secretion. rGRF and hpGRF were both ineffective on SLI and gastrin release while rGRF inhibited and hpGRF stimulated BLI secretion. This effect was not dose related. At luminal pH2 all four peptides stimulated BLI secretion. Stimulation by PHI was already observed at a dose of 10(-14) M while VIP elicited a stimulatory effect at 10(-12) M. PHI at the two lowest concentrations of 10(-14) and 10(-12) M elicited a stimulation of SLI and gastrin release while the same doses of VIP and the higher doses of all four peptides had no effect on SLI and gastrin secretion at an acidic intraluminal pH.(ABSTRACT TRUNCATED AT 250 WORDS)