Release and vasoactive actions of catecholamines during inhibition of prostaglandin synthesis in normal man

Effect of endothelin-1 in man: pretreatment with nifedipine, with indomethacin and with cyclosporine A

The rise in blood pressure following the intravenous administration of endothelin-1 remained unchanged in healthy male volunteers pretreated with either the calcium-channel antagonist nifedipine (10 mg orally), the cyclo-oxygenase inhibitor indomethacin (150 mg day-1 for three days) or the immunosuppressive agent cyclosporine (5 mg kg-1 body weight for five days). Following administration of nifedipine the rise in plasma concentrations of endothelin-1 during the infusion of the peptide was markedly higher (P less than 0.01) than during control experiments without nifedipine. It is concluded that, in healthy men, nifedipine, indomethacin and cyclosporine do not exert a major influence on the pressor action of endothelin-1. However, nifedipine apparently influences the elimination of endothelin-1 from the circulation in healthy men.

Increased secretion of insulin but unchanged secretion of growth hormone in hyperglycaemic type II diabetics treated with acetyl-salicylic acid

The effect of acetyl-salicylic acid (ASA, 3 g/d for three days) on basal and arginine-stimulated concentrations of insulin and growth hormone was studied in seven type II diabetics. From 120 min before until 120 min after the infusion of arginine-hydrochloride (30 g/30 min) blood glucose concentrations were clamped at hyperglycaemic levels both during treatment with ASA (blood glucose: 12.7 +/- 1.2 mmol/l) and during a control experiment without ASA (blood glucose: 12.9 +/- 1.3 mmol/l). Concentrations of serum insulin in the hyperglycaemic state prior to arginine infusion were increased during treatment with ASA, whereas increments of serum insulin induced by i.v. arginine were unaffected. No difference was seen in either basal or stimulated concentrations of growth hormone. Thus, ASA enhances glucose-induced secretion of insulin in type II diabetics but fails to potentiate the glucose-dependent suppression of arginine-stimulated growth hormone release. In contrast to the pancreatic beta-cell the glucose-sensitive regulatory mechanism of growth hormone release appears to be unaffected by the inhibition of endogenous prostaglandin synthesis.