Inhibitory effect of dichlorvos on arterial smooth muscle contraction

The effect of the organophosphate pesticide, dichlorvos, on the contractile responses of isolated rat tail arteries has been studied. Dichlorvos (10(-8)-10(-4) M) had no effect on baseline tension, but relaxed 10(-7) M norepinephrine (NE), 10(-7) M 5-HT or 100 mM KCl contractions dose-dependently. Dichlorvos also inhibited CaCl2 dose-response curves in K+-depolarized strips, as well as depressing both phasic and tonic components of NE-induced contractions. The results suggest a direct relaxant effect of dichlorvos on arterial smooth muscle by a mechanism probably related to interference with Ca2+ supply.