Biochemical studies on the sarcolemmal function in the hypertrophied rabbit heart

Abstract

In order to carry out a biochemical evaluation of the sarcolemma in the hypertrophied myocardium, homogenates were prepared from different parts of the heart of rabbits with experimentally produced aortic constriction. Homogenates of the hypertrophied non-failing left ventricle showed decreased specific activities (expressed per mg protein) of ouabain-sensitive K +-stimulated p-nitrophenylphosphatase (K +-PNPPase, 76% of the control) as well as decreased basal- and fluoride-stimulated ad enylcyclase (73 and 83% of the control respectively). Smaller and less significant changes were observed in homogenates of both non-hypertrophied right ventricles and hypertrophied atria. No change in 5′-nucleotidase activity was observed in the hypertrophied left ventricle. Especially when the activities of K +-PNPPase and F −-stimulated adenylcyclase are compared with 5′-nucleotidase activity a change in sarcolemmal function in hypertrophied left ventricle is highly suggestive. In this study left and right ventricular as well as atrial DNA or hydroxyproline concentrations were recorded to investigate their relationship to protein content and 5′-nucleotidase activity. As expected, in hypertrophied non-failing left ventricle the DNA concentration was significantly decreased (85% of the control). Furthermore the hydroxyproline concentration did not differ from the control and there was no correlation between hydroxyproline concentration and 5′-nucleotidase activity in left ventricle. It could not be excluded that high activities of 5′-nucleotidase in right ventricle and atria (compared with left ventricle) were due to the high connective tissue content in these parts of the heart.