Peptide histidine isoleucine: a secretagogue in human jejunum.

Peptide histidine isoleucine (PHI) is a newly discovered peptide from porcine intestine, which has sequence homologies with VIP, an established intestinal secretagogue. To study the effects of PHI in human jejunum, natural porcine PHI was infused intravenously at 10.7 +/- 1.7 pmol/kg/min (mean +/- SEM) in normal volunteers during steady state perfusion of the jejunum with an isotonic bicarbonate-electrolyte solution. Plasma PHI concentrations rose to 279 +/- 26 pmol/l (mean +/- SEM) in the first 20 minutes of the infusion reaching 417 +/- 45 at 40 minutes. At these concentrations PHI induced a net secretion of chloride and sodium and either decreased net absorption or increased net secretion of fluid and potassium, while bicarbonate transport remained unaffected. Peptide histidine isoleucine is a potent jejunal secretagogue in man.