Vasodilating action of methylhesperidin

The vascular resistance in the hindlimb of anesthetized dogs was measured by constant-rate perfusion. It showed that methylhesperidin (MH) 40 mg/kg iv reduced both vascular resistance and blood pressure. MH 1.6, 3.2, 6.4 mg/kg ia caused a dose-dependent reduction of vascular resistance. The vasodilating action of MH was partially prevented by propranolol 20μg/kg only but neither affected by atropine 50μg/kg nor by diphenhydramine 0.3 mg/kg. MH 3.2 mg/kg did not affect the vasoconstrictive action of methoxamine 2.5μg/kg. NA- and KCl-induced contraction of the rabbit aortic strip was inhibited by MH which made the cumulative dose-response curve of the aortic strip to CaCl2 unparallelly shift rightward. MH inhibited intracellular Ca2+-dependent contraction of the aortic strip induced by NA but failed to suppress the extracellular Ca2+-dependent contraction. It is suggested that MH inhibited the voltage-dependent Ca2+ channel and the release of intracellular Ca2+ by NA.