Enhancement by cytochalasin B of ouabain-stimulated catecholamine secretion from cultured bovine adrenal chromaffin cells: possible relation to alteration in Na+/K(+)-pump activity.
1. Catecholamine secretion evoked by ouabain from cultured bovine adrenal chromaffin cells has previously been shown to be markedly enhanced by pretreatment of the cells with cytochalasin B (Morita et al., 1988). To elucidate a possible mechanism of this enhancement, the stimulatory action of ouabain on Ca2+ influx as well as catecholamine secretion was then examined in the cells pretreated with or without cytochalasin B. The effect of cytochalasin B pretreatment on the inhibitory action of ouabain on the Na+/K+ pump was also examined by measuring 86Rb+ uptake into the cells. 2. Pretreatment of the cells with cytochalasin B caused enhancement of ouabain-induced catecholamine secretion, and this enhancement was accompanied by the elevation of ouabain-stimulated 45Ca2+ uptake into the cells. The inhibitory action of ouabain on 86Rb+ uptake was significantly enhanced by pretreatment of the cells with cytochalasin B under the same conditions. 3. These results indicate that the enhancement of ouabain-induced catecholamine secretion caused by cytochalasin B pretreatment may be due to the increase in ouabain-stimulated Ca2+ influx into the cells and, furthermore, suggest the possibility that this increase in Ca2+ influx may be attributed to the potentiation of the inhibitory action of ouabain on the Na+/K+ pump in the adrenal chromaffin cell. Thus, the present study provides an evidence for a possible role of microfilaments as one of the intrinsic factors modulating the plasma membrane functions.
Morita
K
K
Department of Pharmacology, Tokushima University School of Medicine, Japan.
Hamano
S
S
Oka
M
M
Yoshizumi
M
M
D000313:Adrenal Medulla / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D002838:Chromaffin System; D003571:Cytochalasin B / Q000494:pharmacology*; D005707:Gallic Acid / Q000031:analogs & derivatives; D010042:Ouabain / Q000494:pharmacology*; D012636:Secretory Rate / Q000187:drug effects; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
D002395:Catecholamines; D003571:Cytochalasin B; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D010042:Ouabain; D005707:Gallic Acid; D014700:Verapamil; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium