The role of cation-activated ATPases in transmitter release from the rat iris.
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.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D066298:In Vitro Techniques; D007498:Iris / Q000201:enzymology / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D010477:Perfusion; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D012964:Sodium; D000251:Adenosine Triphosphatases; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine