Abstract
Myosin (M) ATPase activity of contractile proteins (CP) has been shown to be an index of muscle energy utilization. Under certain conditions, a relationship exists between ATPase activity and contractile velocity. In the adult dog, mild chronic systolic pressure overload is associated with increases in M ATPase activity and contractile element velocity. We have previously demonstrated an increase in contractile element velocity (mechanical Vmax) in the left ventricle (LV) of the newborn lamb. To determine the enzymatic response of CP to hemodynamic alterations of the transitional circulation, we examined cardiac M ATPase activity in six lambs and four adult sheep. Tissue was obtained from the lateral wall of the LV; myosin was isolated by previously developed purification techniques utilizing (NH4)2SO4 fractionation of CP. Concentration of pure myosin was determined by the Lowry method and potassium activated ATPase activity was determined by phosphate assay as described by Fiske and SubbaRow. From the data obtained, we calculated enzymatic Vmax values as follows:
The newborn LV responds to increasing demands of the transitional circulation with increases in energy utilization.
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Riemenschneider, T., Brenner, R., Burks, D. et al. MYOCARDIAL CONTRACTILE PROTEINS IN LAMBS: MATURATIONAL CHANGES IN ENZYMATIC FUNCTION. Pediatr Res 11, 398 (1977). https://doi.org/10.1203/00006450-197704000-00173
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DOI: https://doi.org/10.1203/00006450-197704000-00173