The effects of the nitric oxide donors molsidomine and SIN-I on human polymorphonuclear leucocyte function in vitro and ex vivo.

The nitrovasodilator and nitric oxide donor molsidomine and its metabolite SIN-I dilate vascular smooth muscle and inhibit platelet activation by increasing intracellular concentrations of cyclic GMP. We have therefore studied the effects of molsidomine and SIN-I on isolated human polymorphonuclear leucocytes (PMN) in vitro and ex vivo. In vitro molsidomine dose-dependently reduced beta-glucuronidase release and the generation of superoxide anions from non-activated and from FMLP- or PAF-stimulated human PMNs. SIN-I was equally effective in reducing beta-glucuronidase release and totally inhibited oxygen radical generation at a concentration of 580 mumol.l-1. In a double-blind, placebo-controlled, randomized trial we also studied beta-glucuronidase release and the generation of superoxide anions from isolated PMNs. Blood was drawn from 12 healthy volunteers before and 3 h after oral molsidomine (16 mg) or placebo. There was no statistically significant difference in beta-glucuronidase release and superoxide anion formation when the PMNs were isolated before or after molsidomine or placebo. This was the case for non-activated, as well as FMLP- or PAF-stimulated PMNs. Thus, the nitric oxide donors molsidomine and its metabolite SIN-I caused a dose-dependent inhibition of PMN functions in vitro, but no significant inhibition when the PMNs were isolated after oral molsidomine.