A comparison of the relaxant effects of pinacidil in rabbit renal and mesenteric artery

Abstract

1. 1. The relaxant effects of pinacidil were compared in isolated rabbit renal and mesenteric artery. 2. 2. Pinacidil (10 nm–300 μM) relaxed renal and mesenteric arterial rings precontracted with phenylephrine with p D 2 values of 5.11 ± 0.03 and 6.27 ± 0.04, respectively. 3. 3. The inhibitory effect of pinacidil on the rabbit mesenteric artery was competitively antagonized by glibenclamide (1–10 μM). The calculated p K B value was 6.37 ± 0.04. On the renal artery, glibenclamide (2–20 μM) did not significantly affect pinacidil-induced relaxation ( P > 0.05). 4. 4. Tetraethylammonium (TEA, 1–10 mM) competitively antagonized the pinacaidil induced relaxation of the rabbit renal artery. The p K B value was 3.22 ± 0.08. On the mesenteric artery TEA antagonized the effect of pinacidil in a noncompetitive manner. 5. 5. The concentration-response curves for pinacidil on the rabbit renal and mesenteric artery were not affected by apamin (0.1 μM). 6. 6. It is concluded that ATP-sensitivie K + channels (K ATP) are not involved in pinacidil action on the rabbit renal artery. On the contrary, K ATP are probably major sites of pinacidil action on the rabbit mesenteric artery.