The cellular mechanisms involved in the vasodilator effect of nebivolol on the renal artery

Nebivolol is known as a highly selective β1-adrenoceptor antagonist. Based on the reported vasodilator effect of nebivolol, we examined the cellular mechanisms by which the drug induces renal artery vasodilation, an issue of potential relevance for condition associated with high blood pressure. To this purpose, myograph and patch-clamp techniques were used. Small mouse renal arteries were placed in the myograph chamber, and after the optimal concentration for the vasodilator effect of nebivolol was established (50 μM), the arteries were further investigated to assess the potential contribution of nitric oxide (NO) and of Ca2+ ions to the nebivolol-induced effect, by exposing the arteries to the specific inhibitors such as NG-nitro-l-arginine methylester (l-NAME, 100 μM), ethylenglycol-bis-(β-amino-ethylen ester) N,N′-tetraacetic acid (EGTA, 4 μM) and thapsigargin (1 μM). The expression of NO synthase was evaluated by the Western-blot technique. Using myograph and patch-clamp techniques applied on intact renal artery, we investigated the role of β2-adrenoceptors, of myoendothelial junctions and of Ca2+-activated K+ channels in the vasodilatory effects of nebivolol, using 100 μM butoxamine, 40 μM 18 beta-glycyrrhetinic acid, 1 mM tetraethylammonium, and 100 nM iberiotoxin, respectively. The results showed that the cellular mechanisms of the vasodilator effect of nebivolol on the renal artery entail (i) activation of the endothelial β2-adrenoceptor, (ii) participation of [Ca2+]i, (iii) increase in NO and eNOS, and (iv) activation of Ca2+-activated K+ channels. The cellular mechanisms underlying vasodilator effect of nebivolol on the artery explain the favorable effect of this drug in hypertension.