title: Mg2+--Ca2+--Na+ interactions in uterine smooth muscle: studies with cAMP.
abstract: The influence of variation in the extracellular concentrations of Na+, Mg2+, and Ca2+ in the depolarizing medium on isoproterenol-induced increases in cAMP levels and relaxation was studied in rat uterus. Isoproterenol (10(-8) M) failed to increase cAMP levels in the high-K+ medium containing no Na+. When 80 mM Na+ was present in the medium, isoproterenol caused increases in cAMP levels similar to those observed in nondepolarized uterus. A similar effect of 2.5 mM Mg2+ was observed on the cAMP response. These effects of Na+ and Mg2+ were antagonized by increasing the extracellular concentration of Ca2+. The simultaneous presence of 80 mM Na+ and 2.5 mM Mg2+ did not produce an additive effect on the cAMP responses.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology*; D009215:Myometrium / Q000187:drug effects* / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000494:pharmacology*; D014590:Uterine Contraction / Q000187:drug effects; D014599:Uterus / Q000187:drug effects*
chemical_list: D011189:Potassium Chloride; D012964:Sodium; D000242:Cyclic AMP; D008274:Magnesium; D007545:Isoproterenol; D002118:Calcium