The role of cation-activated ATPases in transmitter release from the rat iris
Abstract:
Release of noradrenaline (NA) from isolated rat iris during perfusion in K+-free medium was confirmed. Direct biochemical measurement of different cation-activated ATPases did not reveal any definite relationship between Na+K+ ATPase and NA release. A significant increase in Ca++Mg++ ATPase activity was found on termination of NA release obtained by reintroduction of K+ to the medium. Criticism of the model for studying enzymatic control of transmitter release under physiological conditions is presented. It is suggested that removal of intracellular Ca++ ions by a calcium pump is directly associated with termination of transmitter release.
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