Renal effects of gastrin C-terminal tetrapeptide (as pentagastrin) and cholecystokinin octapeptide in conscious rabbit and man.

Pentagastrin and cholecystokinin octapeptide (CCK8) were infused i.v. at three different doses in two sets of 4 conscious rabbits following a repeated measurements design (130, 1,300 and 13,000 pmol kg-1 min-1 pentagastrin; 5, 50 and 450 pmol kg-1 min-1 CCK8). In man, two different doses of pentagastrin (13 and 65 pmol kg-1 min-1) were infused in two groups of 6 subjects, and CCK8 (2 pmol kg-1 min-1) in a third group. According to published human postprandial levels, plasma CCK8-like immunoreactivity concentrations were supraphysiological at all doses infused. In the rabbit, pentagastrin produced a dose-related fall in urine flow and free water clearance, but no significant change in systemic and renal haemodynamics, electrolyte excretion and measured plasma constituents; however, in human subjects, pentagastrin increased renal sodium excretion and reduced potassium excretion but did not change glomerular filtration rate. In the rabbit, CCK8 produced a dose-related fall in plasma renin activity, plasma calcium concentration and mean arterial blood pressure; dose-dependent increases in effective renal plasma flow, glomerular filtration rate and renal sodium excretion. In man, changes in sodium and potassium excretion similar to pentagastrin were observed; there were no significant changes in plasma renin activity, plasma calcium concentration, blood pressure, effective renal plasma flow or glomerular filtration rate. The pharmacological renal effects of pentagastrin in conscious water-loaded rabbits resemble vasopressin. In contrast, CCK8's most striking effect was vasodilatation and was unusual in inhibiting rather than stimulating renin release. In man the net changes in urine composition found during infusion of these peptides are similar to those produced by the potassium-sparing diuretics, amiloride and triamterene. However the generally weak renal effects observed, even at pharmacological doses, indicate that these peptides are unlikely to influence renal function under normal physiological conditions.