The differential release of basal ATPase, Ca2+-dependent ATPase, 5′-nucleotidase and cholesterol during homogenization of skeletal muscle

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Abstract
The influence of homogenization times on the presence of constituents in the microsomal fraction of skeletal muscle was investigated. Membranes having Ca2+-activated ATPase activity have a fragmentation pattern distinct from that of membranes displaying Ca2+-independent or basal ATPase activity. These latter membranes were found in highest specific concentration in the microsomal fraction prepared from homogenates subjected to short periods of homogenization. 5''-Nucleotidase activity paralleled that of basal ATPase on short periods of homogenization, as did the specific concentration of cholesterol. Longer periods of homogenization led to a decrease in the specific activity of basal ATPase, which reached its lowest value at 120 s of homogenization, whereas the specific activity of of 5''-nucleotidase and the specific concentration of cholesterol decreased initially in a similar manner to basal ATPase, but both increased substantially after the longest period of homogenization.