title: Sarcolemmal Ca2+-binding and enzyme activities in myocardium from hypothyroid rat.
abstract: Effects of hypothyroidism on heart sarcolemmal activities were examined by using membrane preparations obtained by two different methods from rats treated with propylthiouracil for 6 to 8 weeks. ATP-independent Ca2+ binding, sialic acid and phospholipid content, Ca2+ ATPase, Mg2+ ATPase and adenylate-cyclase were not altered in membranes isolated by the hypotonic shock-LiBr treatment method from hypothyroid hearts. On the other hand, depressed activities of ouabain sensitive Na+-K+ ATPase and 5'-nucleotidase were observed in this hypothyroid preparation. Sarcolemma isolated by the sucrose density gradient procedure from hypothyroid hearts exhibited lower ouabain-sensitive Na+-K+ ATPase and higher ATP-dependent Ca2+ binding as well as Ca2+ stimulated ATPase without any changes in the 5'-nucleotidase, adenylate cyclase and Mg2+-ATPase activities. The activation of ATP-dependent Ca2+ binding and Ca2+ stimulated ATPase by calmodulin in the hypothyroid preparation was greater than the control; these effects of calmodulin were blocked by trifluoperazine. The results suggest some specific changes in the heart sarcolemmal Ca2+-pump during the development of hypothyroidism.
mesh_terms: D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D007037:Hypothyroidism / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*; D019158:N-Acetylneuraminic Acid; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012508:Sarcolemma / Q000201:enzymology*; D012794:Sialic Acids / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D010743:Phospholipids; D012794:Sialic Acids; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D019158:N-Acetylneuraminic Acid; D002118:Calcium