Vasorelaxing effect of the potassium (K+)-channel opener pinacidil in isolated porcine ciliary arteries

purpose: The aim of this study was to investigate the vasorelaxing properti es of pinacidil (a potassium-channel-opener) in isolated porcine ciliary ar teries. Methods: Isometric contractions of isolated porcine ciliary arteries were m easured with a myograph system. The vessels were first precontracted with t he thromboxane A(2) analog U 46679 (0.1 muM), and then exposed, in a cumula tive manner, to increasing concentrations of pinacidil (1 nM-100 muM). Rela xations have been expressed in percent of the maximal contraction evoked by U 46619 (0.1 muM). Results: Pinacidil showed a pronounced concentration-dependent relaxing eff ect in isolated porcine ciliary arteries. The difference between pinacidil and time-control experiments was significant (100 muM: 112 +/-2% vs. 18 +/- 6%, P<0.0001), The half-maximal concentration (pD(50)) value was 5.3 <plus/ minus> 0.1 (- log M). Conclusions: The present study indicates that pinacidil has marked vasorela xing properties in isolated porcine ciliary arteries.