CHANGES IN MYOSIN ISOZYME DISTRIBUTION INDUCED BY LOW-DOSES OF ISOPROTERENOL

  • 1 January 1982
    • journal article
    • research article
    • Vol. 260  (1) , 159-164
Abstract
The Ca2+-activated myosin ATPase activity in isoproterenol-induced hypertrophied left ventricle increased by 20-30%, while in Goldblatt rats hypertrophy occurred with a decreased myosin ATPase activity. In non-dissociating (pyrophosphate) gel electrophoresis, isoproterenol treatment showed decreased V2 and V3 myosin isozymes; at the higher dose of isoproterenol (0.5 mg/kg body wt), only V1 was present. In contrast, a shift toward the V3 isozyme is present in the ventricles of Goldblatt rats. One group of rats was treated with toxic doses of digitoxin; no hypertrophy occurred, but there was a disappearance of V1 and V2 isozymes and a 50% decrease in Ca2+-activated ATPase activity. Low doses of isoproterenol produce hypertrophy with an isozyme pattern similar to that found in young (.apprx. 4-6 wk old) rats. The results with digitoxin show that shifts in the cardiac isozyme distribution can occur without hypertrophy.