Smooth Muscle Relaxant Activity of a Synthetic Dihydropyrimidine Derivative 5-acyl-6-methyl-4(2,3methylenedioxy)phenyl-2-s-benzyl-1,4-dihydro Pyrimidine (bk- vii) on Isolated Rat Uterus and Rabbit Aortic Strip

Abstract

ObjectivesTo investigate the smooth muscle relaxant activity of a newly synthesised dihydropyrimidine derivative 5-acyl-6-methyl-4(2,3 methylenedioxy) Phenyl-2-S-benzyl-1,4-dihydropyrimidine(code named as BK- VII) and comparing with nifedipine on isolated rat uterus and rabbit aortic strip.Effect of the test compound BK-VII on the smooth muscles of isolated rat uterus and isolated rabbit aortic strip was observed and compared with that of nifedipine. Observations were made with increasing bath concentrations of BK-VII and nifedipine. Six preparations were used for each dose of BK-VII and nifedipine. Mean effect of increasing doses of BK-VII and nifedipine on the height of calcium (Ca²⁺) induced contraction of depolarised isolated rabbit aortic strip and on potassium (K⁺) induced contraction of isolated rat uterus were noted and median inhibitory concentration (IC-50) calculated.ResultsTest compound BK-VII had a significant dose-dependent relaxant effect on K⁺-induced contractions of isolated rat uterus. Significant relaxation was seen at bath concentration starting from 4.2X10⁻⁵M (IC₅₀ -12.2X10⁻⁵M). Nifedipine showed significant relaxation at all bath concentrations starting from 2.8X10⁻⁷M (IC₅₀-7.5X10⁻⁷M). Compound BK-VII produced potentiation of Ca²⁺-induced contractions of K⁺-depolarized rabbit's aortic strip at bath concentration of 0.6X10⁻⁵M while significant inhibition was observed at higher bath concentrations. Nifedipine showed dose-dependent significant inhibition at all bath concentrations.BK-VII has a calcium channel blocking activity like nifedipine and it can inhibit the Ca²⁺ dependent contractions of smooth muscles of uterus and aorta.