In a rabbit model of aortic insufficiency, chronic but not acute volume overload leads to decreased myofibrillar ATPase activity, which correlates with disease duration rather than overt heart failure symptoms.
No immediate clinical implications in aortic insufficiency; leaves open ATPase as mechanistic target in chronic volume overload models.
Experimental heart hypertrophy with or without failure was induced in rabbits by aortic insufficiency without thoracotomy. Heart myofibrillar ATPase measured with azide was normal in animals with recent aortic insufficiency sacrificed before the 10th day and low in chronic animals. Enzymatic activity was correlated with the duration of aortic insufficiency, but no clear relationship was observed with symptoms of failure. Natural actomyosin ATPase was measured with a low and a high ionic strength medium and was normal in chronic and recent insufficiency. Superprecipitation of actomyosin and EGTA sensitivity of Mg-ATPase were also normal. Myofibrillar content in adenylate kinase and nucleotidase was very low. RNA of the first pellet obtained after actomyosin extraction was high in recent insufficiency and also in animals killed after the third month.
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Swynghedauw et al. (1971) studied this question.
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