A Comparison of Sarcoplasmic Reticulum Function in Fast and Slow Skeletal Muscle Using Crude Homogenate and Isolated Vesicles
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Sarcoplasmic reticulum vesicles (FSR) were isolated from relatively homogeneous muscle samples representative of type I, IIA, and IIB fibers and Ca2+ uptake (Vmax and total capacity) determined. Crude homogenates of these same fiber populations were also assayed for Ca2+ uptake and the results compared to the FSR values. Both techniques produced qualitatively similar results and demonstrated distinct fiber type differences in both the rate and extent of Ca2+ uptake. The results obtained support the contention that the crude homogenate technique accurately reflects the activity of the sarcoplasmic reticulum.