title: Effects of thyroxine treatment on the hepatic plasma membrane ATPase activity in rats.
abstract: The effects of T4 and T3 upon ATPase activity of plasma membrane preparations produced by different methods has been studied. Media without Na+ or K+ was used to identify Mg++ activated ATPase, and media containing 100-120 mM Na+ and 20-30 mM K+ in addition to Mg++ was used to identify the augmented activity of Na-K ATPase. We also utilized media containing Na+, K+, and Mg++ in the presence and absence of ouabain to identify the Na+-K+ activation. We found no effect of doses of thyroxine in the physiologic range upon the Na+-K+ ATPase activity. A dose-response study indicated that high doses of T4 may stimulate Mg++ activated ATPase. In the P2 preparation of the Touster method we found minimally enhanced Na+-K+ ATPase activity. The quantity of T4 needed to cause such enhancement is approximately 50 times the physiologic replacement dose needed to restore thyroidectomized animals to a euthyroid state. We conclude that thyroid hormones do not stimulate Na+-K+ ATPase of plasma membranes when administered in a physiologic quantity, but may enhance Mg++ atpase activity when administered in a pharmacologic or toxic quantity.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013965:Thyroidectomy; D013974:Thyroxine / Q000494:pharmacology*; D014284:Triiodothyronine / Q000494:pharmacology
chemical_list: D014284:Triiodothyronine; D010042:Ouabain; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase; D013974:Thyroxine