Different Potassium Channels are Involved in Relaxation of Rat Renal Artery Induced by P1075

The ATP-sensitive K+ channels opener (KATPCO), P1075 [N-cyano-N'-(1,1-dimethylpropyl)-N?-3-pyridylguanidine], has been shown to cause relaxation of various isolated animal and human blood vessels by opening of vascular smooth muscle ATP-sensitive K+ (KATP) channels. In addition to the well-known effect on the opening of KATP channels, it has been reported that vasorelaxation induced by some of the KATPCOs includes some other K+ channel subtypes. Given that there is still no information on other types of K+ channels possibly involved in the mechanism of relaxation induced by P1075, this study was designed to examine the effects of P1075 on the rat renal artery with endothelium and with denuded endothelium and to define the contribution of different K+ channel subtypes in the P1075 action on this blood vessel. Our results show that P1075 induced a concentration-dependent relaxation of rat renal artery rings pre-contracted by phenylephrine. Glibenclamide, a selective KATP channels inhibitor, partly antagonized the relaxation of rat renal artery induced by P1075. Tetraethylammonium (TEA), a non-selective inhibitor of Ca2+-activated K+ channels, as well as iberiotoxin, a most selective blocker of large-conductance Ca2+-activated K+ (BKCa) channels, did not abolish the effect of P1075 on rat renal artery. In contrast, a non-selective blocker of voltage-gated K+ (KV) channels, 4-aminopyridine (4-AP), as well as margatoxin, a potent inhibitor of KV1.3 channels, caused partial inhibition of the P1075-induced relaxation of rat renal artery. In addition, in this study, P1075 relaxed contractions induced by 20 similar to mM K+, but had no effect on contractions induced by 80 similar to mM K+. Our results showed that P1075 induced strong endothelium-independent relaxation of rat renal artery. It seems that KATP, 4-AP- and margatoxin-sensitive K+ channels located in vascular smooth muscle mediated the relaxation of rat renal artery induced by P1075.