title: Corticosterone and triiodothyronine control of myocardial Na+-K+-ATPase activity in rats.
abstract: Experiments were carried out to examine the effects of corticosterone and triiodothyronine on rat myocardial Na+-K+-ATPase activity. Corticosterone increased Na+-K+-ATPase activity when administered intravenously in multiple doses, a single dose, and different dosages. The possibility that enhancement of myocardial Na+-K+-ATPase activity by corticosterone is mediated by early changes in intracellular Na+ and K+ was investigated. Following a single dose of corticosterone (1 mg/100 g body wt), the increase in Na+-K+-ATPase activity preceded the changes in intracellular Na+ and K+. Corticosterone did not change the transition temperature and activation energy of the reaction in myocardial Na+-K+-ATPase. This implies that corticosterone does not act by altering the lipid matrix in the microenvironment of the Na+-K+-ATPase system. The interaction between the effects of corticosterone and triiodothyronine on myocardial Na+-K+-ATPase activity was examined. Our studies indicated that corticosterone and triiodothyronine regulate Na+-K+-ATPase activity via parallel independent pathways.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000315:Adrenalectomy; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D003345:Corticosterone / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D011188:Potassium / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013816:Thermodynamics; D013965:Thyroidectomy; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D014284:Triiodothyronine; D003907:Dexamethasone; D012964:Sodium; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D003345:Corticosterone