HUMAN UMBILICAL VESSELS - RESPONSES TO AGENTS FREQUENTLY USED IN OBSTETRIC PATIENTS

OBJECTIVE: Our purpose was to study the effects of some drugs frequent ly used in pregnant women on isolated human umbilical artery and vein segments. STUDY DESIGN: Umbilical artery and vein rings from normal te rm pregnancies were mounted in Krebs-bicarbonate solution in organ bat hs for isometric tension recording. Rings were contracted with potassi um chloride (60 mmol/L) or U46619 (10(-8) mol/L) and then exposed to c umulative concentrations of nimodipine, nifedipine, nicardipine, pheny toin, magnesium sulfate, and hydralazine. Concentration-response curve s were constructed by means of the difference in the percent relaxatio n between test and control vessels. Data analysis was by repeated meas ures analysis of variance, Newman-Keuls test, and the unpaired Student t test as appropriate. A value of p < 0.05 was considered statistical ly significant. RESULTS: All the agents studied were effective umbilic al vasodilators, except for hydralazine, which had minimal effect. The dihydropyridine calcium antagonists were more potent vasodilators tha n were the other agents studied. Nifedipine was the most potent calciu m blocker and was the only dihydropyridine that relaxed the umbilical vein to a greater extent than the umbilical artery. CONCLUSION: The mo st commonly used drugs in preeclampsia have variable effects on the um bilical vessels.