title: Magnesium sulfate-induced relaxation of uterine arteries from pregnant and nonpregnant patients.
abstract: The effects of magnesium sulfate at different concentrations were investigated in isolated rings of uterine arteries from pregnant and nonpregnant patients. Addition of magnesium sulfate (0.5 to 9.6 mmol/L) to the suffusion medium containing the normal concentration of 1.2 mmol/L magnesium sulfate produced concentration-dependent relaxation of norepinephrine (1 mumol/L)-induced or potassium chloride (35 mmol/L)-induced contractions. Magnesium sulfate was about three times more potent in causing inhibition of potassium chloride-induced contractions in uterine arteries from pregnant patients than in those from nonpregnant patients. The concentrations that inhibited 50% of the contraction induced by potassium chloride were 0.6 +/- 0.2 mmol/L (n = 4) in the arteries from pregnant patients and 1.6 +/- 0.2 mmol/L (n = 4) in the arteries from nonpregnant patients. At high concentrations (4.8 and 9.6 mmol/L), magnesium sulfate also was more potent in inhibiting norepinephrine-induced contractions in arteries from pregnant women than in arteries from nonpregnant women. The magnesium sulfate-induced relaxation was almost completely inhibited by calcium chloride (2 mmol/L) added to the suffusion medium containing the normal concentration of 2.5 mmol/L calcium chloride but was not affected by indomethacin (5 mumol/L), methylene blue (10 mumol/L), or removal of the endothelium. The results show that magnesium sulfate, at therapeutic blood concentrations, acts as a potent dilator of human uterine arteries, especially those from pregnant patients. The results are consistent with the view that magnesium sulfate may facilitate uteroplacental perfusion.
authors.affiliation: Department of Anesthesiology, University of Texas Medical Branch, Galveston 77550.
authors.forename: S H
authors.initials: SH
authors.lastname: Nelson
authors.forename: M S
authors.initials: MS
authors.lastname: Suresh
mesh_terms: D000328:Adult; D001158:Arteries / Q000187:drug effects*; D002122:Calcium Chloride / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004336:Drug Antagonism; D004727:Endothelium / Q000502:physiology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008278:Magnesium Sulfate / Q000494:pharmacology*; D008751:Methylene Blue / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011247:Pregnancy; D014599:Uterus / Q000098:blood supply*; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
chemical_list: D011189:Potassium Chloride; D008278:Magnesium Sulfate; D002122:Calcium Chloride; D008751:Methylene Blue; D009638:Norepinephrine; D007213:Indomethacin