Gaining access to the site of exocytosis in bovine adrenal medullary cells.
1. A new technique is described for gaining access to the intracellular site at which exocytosis is controlled. By exposing isolated cells to high electric fields of brief duration, it is possible to create "leaky" cells in which the plasma membrane has been by-passed without impairing the ability of the cells to undergo exocytosis. 2. In the presence of EGTA and an ionized Ca of less than 10(-8) M, "leaky" cells lose less than 1% of their total catecholamine. When exposed to 10 microM ionized Ca they lose up to 30% of their catecholamine together with dopamine-beta-hydroxylase but no lactate dehydrogenase. The time course of release of both catecholamine and dopamine-beta-hydroxylase are identical, suggesting that release must involve exocytosis. Exocytosis in these "leaky" cells has the following properties: A) It is half maximal in the presence of a buffered ionized Ca of approximately 1 microM. Millimolar concentrations of Mg reduce both the affinity for Ca and also the total amount of catecholamine released at high calcium concentrations. B) It has a specific requirement for Mg ATP. C) It is inhibited by a variety of anions. The most potent inhibitor is SCN, and the least glutamate and acetate. D) It is inhibited by the anti-psychotic drug trifluoperazine.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000313:Adrenal Medulla / Q000166:cytology*; D000818:Animals; D002118:Calcium / Q000502:physiology; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000502:physiology; D005089:Exocytosis; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology
D002395:Catecholamines; D000255:Adenosine Triphosphate; D008274:Magnesium; D002118:Calcium