Clotrimazole is a potent vasodilator of the rat coronary microcirculation.
Clotrimazole (CLT), used in the treatment of patients with sickle cell disease, directly blocks Ca2+-activated K+ (K+<INF POS="STACK">Ca) channels in red cells and in portal vein smooth muscle cells by a cytochrome P450(cyt P450)-independent mechanism. Therefore, we examined the effects of CLT on vasomotor tone of coronary arterioles. Rat coronary arterioles (80-180 micro(m) in diameter) were studied in vitro in a pressurized no-flow state with a video microscopy. CLT (0.1 micromol/L) elicited in nonprecontracted vessels a small contraction (<10% baseline diameter, P < 0.05 vs time control), consistent with blockade of a hyperpolarizing K+ channel. However, similar contraction was produced by the cyt P450 blocker 17-octadecynoic acid (17-ODYA, 100 micromol/L), suggesting possible involvement of arachidonate metabolites of cyt P450. In contrast, microvessels precontracted with the thromboxane A2 analog U46619 dilated in response to CLT [>90% relaxation of the U46619-induced precontraction at 100 micromol/L (P < 0.01 vs time control)] and its structural analogs flutrimazole (FLT), UR-4055, UR4057, UR-4058, and UR-4059. This relaxation was cyt P450-independent, since the in vivo CLT metabolite (CLT-carbinol) was equipotent with CLT, and 17-ODYA did not promote relaxation. CLT-induced dilation was not inhibited by the nitric oxide synthase inhibitor NGnitro-l-arginine (100 micromol/L, P > 0.5) or affected by endothelial denudation (P > 0.5). Thus, CLT at concentrations >1 micromol/L is a potent vasodilator of rat coronary arterioles. This dilation is likely mediated through a vascular smooth muscle mechanism independent of cyt P450 and is not modulated by nitric oxide or by the endothelium. This effect may arise from CLT's reported ability to inhibit voltage-gated Ca2+ channels or to inhibit, in some tissues, Ca2+ release from intracellular stores. The CLT- and FLT-induced relaxation may be a property common to this class of drugs and have clinical applicability.
Department of Surgery, Harvard Medical School, Boston, Massachusetts, 02215, USA.
M
M
Tofukuji
C
C
Metais
S Y
SY
Wang
S L
SL
Alper
F W
FW
Sellke
D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology*; D003022:Clotrimazole / Q000031:analogs & derivatives / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects*; D008833:Microcirculation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*
D000935:Antifungal Agents; D014665:Vasodilator Agents; D003022:Clotrimazole