title: Effects of magnesium chloride on the contractile response of uterus to several agonists in Ca-free solution.
abstract: The effects of MgCl2 on the oestrogen-dominated rat uterus have been examined. Tissues were preincubated in a Ca2+- and Mg2+-free medium containing 3 mM EDTA. Most experiments were subsequently performed in a similar medium containing either no EDTA or EDTA (1 mM). When MgCl2 was added cumulatively (1-32 mM) no contractile responses were obtained in Ca,Mg-free medium or in Ca,Mg-free high K+ solution. When 2 mM CaCl2 was added, a sustained contraction was obtained. Subsequent addition of cumulative concentrations of MgCl2 caused concentration-dependent relaxation. Oxytocin, 2 microM, produced a small and sustained contraction in a Ca,Mg-free medium. Addition of MgCl2, 2 mM, increased this contraction. In a Ca,Mg-free medium vanadate (8 X 10(-5)M) did not evoke spasm of uterine smooth muscle. After addition of MgCl2 in cumulative amounts (1-32 mM) in the presence of vanadate, a concentration-dependent contraction was obtained. The present work shows that in Ca-free solution, maintained contractions induced by oxytocin and vanadate are augmented by Mg2+.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D004492:Edetic Acid / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology*; D015636:Magnesium Chloride; D010121:Oxytocin / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014590:Uterine Contraction / Q000187:drug effects*; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology
chemical_list: D014639:Vanadium; D015636:Magnesium Chloride; D014638:Vanadates; D010121:Oxytocin; D011189:Potassium Chloride; D004492:Edetic Acid; D008274:Magnesium; D002118:Calcium