Peptide histidine valine: its haemodynamic actions and pharmacokinetics in man differ from those of vasoactive intestinal peptide and peptide histidine methionine

1. The effects of intravenous and intra-arterial infusion of the peptides derived from prepro-vasoactive intestinal peptide, vasoactive intestinal peptide, peptide histidine methionine and peptide histidine valine, were examined in six healthy volunteers. 2. Vasoactive intestinal peptide given intravenously caused a significant increase in heart rate and a decrease in diastolic, but not systolic, blood pressure, whereas peptide histidine valine caused an increase in heart rate alone, despite higher achieved circulating peptide concentrations. Peptide histidine methionine did not affect heart rate or blood pressure. Forearm blood flow was increased by vasoactive intestinal peptide and peptide histidine valine when infused locally intra-arterially, although vasoactive intestinal peptide was more potent than peptide histidine valine. 3. Plasma concentrations of cardiodilatin (the N-terminal peptide derived from pro-atrial natriuretic peptide) were increased by intravenous infusion of vasoactive intestinal peptide, but were unaffected by peptide histidine methionine or peptide histidine valine. Circulating plasma concentrations of adrenaline and noradrenaline did not change during infusion of vasoactive intestinal peptide, peptide histidine methionine or peptide histidine valine. 4. Peptide histidine valine had a long half-life when compared with peptide histidine methionine and vasoactive intestinal peptide. 5. We conclude that peptide histidine valine is active in the human cardiovascular system and has a similar, though less potent, vasodilating action to vasoactive intestinal peptide. The higher circulating levels of peptide histidine valine found in man suggest that it may be important in modulating vascular tone.

Effects of preprovasoactive intestinal polypeptide-derived peptides on ileal output

Tumors associated with the Verner Morrison syndrome secrete peptide histidine methionine, its C-terminally extended variant peptide histidine valine, and vasoactive intestinal peptide. There is evidence that vasoactive intestinal peptide mediates diarrhea, but recent evidence suggested that peptide histidine methionine and peptide histidine valine may be at least as important. Infusion of vasoactive intestinal peptide, peptide histidine methionine, and peptide histidine valine into patients with ileostomies produced mean plateau plasma levels of 163, 1301, and 2106 pM, respectively, which are within the range seen in the Verner Morrison syndrome. Vasoactive intestinal peptide produced an integrated ileal output of 174 (53) g (mean [SEM]), compared with only 20 (7) g with peptide histidine methionine and 10 (3) g with peptide histidine valine. These results suggest that vasoactive intestinal peptide is substantially more important than peptide histidine methionine or peptide histidine valine in mediating diarrhea in the Verner Morrison syndrome.

The distribution, purification, and pharmacological action of an amphibian neuromedin U

The distribution, primary structure, and relative biological activity of neuromedin U has been determined from the frog Rana temporaria. Following sequential column chromatography of a gastrointestinal extract, the peptide was sufficiently pure to enable characterization by micro-sequence analysis. The entire sequence was found to be an icosapentapeptide which displays marked sequence similarity to both porcine and rat neuromedin U. The sequence of the biologically active, COOH-terminal region is almost completely conserved across all species. Synthetic, COOH-terminally amidated amphibian neuromedin U, like the porcine and rat peptides, stimulates rat uterine contraction in vitro thereby fulfilling the criterion upon which the nomenclature of this peptide family is based. In addition, the peptide demonstrates parallel pressor effects when infused systemically into rats. The high degree of amino acid sequence conservation is indicative of strong evolutionary pressure acting to retain the presence of this possibly physiologically important peptide across the vertebrate subphylum.

Purification and characterisation of cerebellins from human and porcine cerebellum

The primary human and porcine structure of the novel neuropeptide cerebellin is unknown. These peptides were, therefore, isolated by a combination of ion-exchange and reverse-phase chromatography using a specific radioimmunoassay against rat cerebellin. The sequences of the peptides were deduced by mass spectrometry (for both human and porcine cerebellins) and gas-phase Edman degradation (for porcine cerebellin). In both species, two molecular forms were identified. In the human, the major form corresponded to the pentadecamer [des-Ser1]-cerebellin (approximately 95% of the total) and the minor form, to the hexadecamer peptide. In the pig, however, both molecular forms were present in approximately equal amounts. The finding that the sequences of human and porcine cerebellin are identical to that of the rat suggests that strong evolutionary pressure has acted to conserve this sequence.

Peptide histidine valine-42 stimulates gastric acid secretion in man

The effect of peptide histidine valine-42 (PHV-42) on gastric acid secretion was studied in man. PHV-42 was infused into 5 healthy volunteers at a dose of 10 pmol/kg/min. This dose caused a significant stimulation of basal gastric acid and potassium output. There were no significant changes in circulating gastrin throughout the infusion. In 2 subjects with a background of submaximal pentagastrin stimulation, PHV-42 infusion at the same dose did not alter acid secretion in either subject. The previous observation that PHV-42 is found particularly in the stomach and the new finding that it stimulates basal gastric secretion suggest the possibility that PHV-42 could have a role in local control of acid secretion.

Effects of prepro-vasoactive intestinal polypeptide-derived peptides on net fluid flux in small intestine of anesthetized rats

Intravenous infusion of low doses of vasoactive intestinal polypeptide, peptide histidine valine-42, and peptide histidine methionine (and the rat equivalent, peptide histidine isoleucine) into anesthetized rats caused a reduction in net absorption of fluid from the small intestine. Larger doses caused a net fluid secretion. At the same nominal infusion rates, peptide histidine valine-42 appeared to be the most potent. In terms of plasma concentrations achieved, however, vasoactive intestinal polypeptide was approximately six times more active than the other two human peptides. If confirmed in humans, these results would suggest that peptide histidine methionine and peptide histidine valine may be as important as vasoactive intestinal polypeptide in causing the watery diarrhea seen in the Verner-Morrison syndrome in which plasma levels of all three peptides are raised.

Infusion of prepro-VIP derived peptides in man: effect on secretion of prolactin

Infusion of the three human prepro-VIP derived peptides [vasoactive intestinal peptide (VIP), peptide histidine methionine (PHM) and the newly discovered peptide histidine valine (PHV-42)] at a constant nominal rate of 5 pmol/kg/min in 6 healthy volunteers for 60 min resulted in plateau plasma levels of 56,475 and 1,052 pmol/l, respectively. Although these values were above those found in the circulation under physiological conditions, only VIP caused a significant rise of prolactin (PRL) during, and postinfusion. Circulating luteinizing hormone and cortisol concentrations remained unchanged. As peptide histidine isoleucine, the porcine equivalent of PHM, has been postulated to be a potent hypophyseal portal pituitary PRL-releasing factor in the rat, we suggest that in man, VIP is more active than either PHM or PHV-42, and is likely to be a better candidate.