title: Human umbilical vessels: responses to agents frequently used in obstetric patients.
abstract: OBJECTIVE
  Our purpose was to study the effects of some drugs frequently used in pregnant women on isolated human umbilical artery and vein segments.
  
  
  METHODS
  Umbilical artery and vein rings from normal term pregnancies were mounted in Krebs-bicarbonate solution in organ baths for isometric tension recording. Rings were contracted with potassium chloride (60 mmol/L) or U46619 (10(-8) mol/L) and then exposed to cumulative concentrations of nimodipine, nifedipine, nicardipine, phenytoin, magnesium sulfate, and hydralazine. Concentration-response curves were constructed by means of the difference in the percent relaxation between test and control vessels. Data analysis was by repeated measures analysis of variance, Newman-Keuls test, and the unpaired Student t test as appropriate. A value of p < 0.05 was considered statistically significant.
  
  
  RESULTS
  All the agents studied were effective umbilical vasodilators, except for hydralazine, which had minimal effect. The dihydropyridine calcium antagonists were more potent vasodilators than were the other agents studied. Nifedipine was the most potent calcium blocker and was the only dihydropyridine that relaxed the umbilical vein to a greater extent than the umbilical artery.
  
  
  CONCLUSIONS
  The most commonly used drugs in preeclampsia have variable effects on the umbilical vessels.
authors.affiliation: Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Belfort
authors.forename: G R
authors.initials: GR
authors.lastname: Saade
authors.forename: M
authors.initials: M
authors.lastname: Suresh
authors.forename: D
authors.initials: D
authors.lastname: Johnson
authors.forename: Y P
authors.initials: YP
authors.lastname: Vedernikov
mesh_terms: D000704:Analysis of Variance; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004095:Dihydropyridines / Q000494:pharmacology; D005260:Female; D006801:Humans; D006830:Hydralazine / Q000494:pharmacology; D066298:In Vitro Techniques; D008278:Magnesium Sulfate / Q000494:pharmacology; D010672:Phenytoin / Q000494:pharmacology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000188:drug therapy*; D014469:Umbilical Arteries / Q000187:drug effects* / Q000502:physiology; D014471:Umbilical Veins / Q000187:drug effects* / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects
chemical_list: D002121:Calcium Channel Blockers; D004095:Dihydropyridines; D006830:Hydralazine; D010672:Phenytoin; D008278:Magnesium Sulfate