Rat myometrial Na/K ATPase is increased by serum but not by isoproterenol and relaxin.
1. Na/K ATPase activity in rat myometrial cells in culture exhibited a Kapp of 0.93 mM for Rb+ and a Ki of 31 microM for ouabain with respect to Rb+. 2. 86Rb+ uptake was stimulated by serum and monensin but was not affected by the uterine relaxants isoproterenol and relaxin in 0.5-7.5 mM Rb+. Nonetheless, these relaxants elicited significant increases in 45Ca2+ efflux under similar conditions. 3. These data suggest that increased Na/Ca exchange resulting from a stimulation of Na/K ATPase is not involved in the mechanism of action of relaxin and isoproterenol in the uterus.
Sanborn
B M
BM
Department of Biochemistry and Molecular Biology, University of Texas Medical-School, Houston 77030.
D000818:Animals; D001790:Blood Physiological Phenomena; D002132:Calcium Radioisotopes; D005260:Female; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008985:Monensin / Q000494:pharmacology; D009215:Myometrium / Q000187:drug effects / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012065:Relaxin / Q000494:pharmacology*; D012414:Rubidium Radioisotopes; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D002132:Calcium Radioisotopes; D012414:Rubidium Radioisotopes; D010042:Ouabain; D012065:Relaxin; D008985:Monensin; D000254:Sodium-Potassium-Exchanging ATPase; D007545:Isoproterenol