NONHOMOGENEOUS CA RELEASE IN ISOLATED FROG SKELETAL-MUSCLE FIBERS

We have examined the spatial distribution of [Ca2+] during tetanic sti mulation in frog skeletal muscle cells using a fluorescence imaging me thod. We have found a completely unexpected pattern of Ca release: Ca is released forming gradients composed of spots of very significant an d slow fluctuations of calcium release. Our findings could be explaine d if the calcium release process in skeletal muscle is influenced sign ificantly by [Ca2+](i), such as in cardiac muscle, and suggests that t he SR/Ca release control can include the established voltage-dependent plus a cardiac-like process of calcium-induced Ca release and a Ca re lease inhibition by Ca.