CHARACTERISTICS OF THE ANTIVASOCONSTRICTOR EFFECT OF PINACIDIL ON ISOLATED RADIAL ARTERY

Pinacidil, a prevously studied potassium channel opener (PCO), is a potent antihypertensive agent in animals and humans. Its mechanism of action is not completly defined. The aim of our study was to investigate the antivasoconstricting effect of pinacidil on the isolated RA and to study whether this effect is endothelium-dependent. Contractions of isolated RA rings with intact endothelium were provoked by electrical field stimulation (EFS, 20 Hz) or exogenously applied noradrenaline (NA, 10 _M). Pinacidil (10 nM-0.1 mM) produced a concentration-dependent inhibition of both EFS- and NA-evoked contractions (p>0.05). NO synthesis inhibitor, L-NAME (10 _M) and the guanylate cyclase inhibitor, methylene blue (10 _M) did partly antagonize NA-evoked contractions and were without effect on EFSinduced contractions. Thus, the antivasoconstrictor effect of pinacidil on RA is partly endothelium-dependent and probably mediated via cGMP-dependent NO-pathway.