Arachidonic acid-induced LH release is ATP-independent and insensitive to N-ethyl maleimide.
The mechanism of arachidonic acid (AA)-induced LH release was characterized using sheep pituitary cells in primary culture permeabilized with Staphylococcal alpha-toxin. In intact cells, exogenous AA evoked release of LH in a manner which was partially dependent on extracellular Ca2+. At similar concentrations, AA also caused cell permeabilization as monitored by efflux of [3H]2-deoxyglucose metabolites. In alpha-toxin-permeabilized cells where cytosolic Ca2+ was clamped at resting levels, AA retained its ability to cause LH release. Unlike the stimulation of exocytosis produced by Ca2+, phorbol ester or cyclic AMP, AA-evoked release was independent of ATP and was not inhibited by pretreatment with N-ethyl maleimide. These findings indicated that exogenous AA does not cause LH release by Ca2+ influx or mobilization or by activating protein kinase C. The results suggest that LH release induced by exogenous AA is probably due to its detergent-like properties, and does not represent true exocytosis.
Kaye
P V
PV
Department of Chemical Pathology, University of Cape Town Medical School, Observatory, South Africa.
van der Merwe
P A
PA
Millar
R P
RP
Davidson
J S
JS
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005033:Ethylmaleimide / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000096:biosynthesis*; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*; D012756:Sheep / Q000378:metabolism*
D016718:Arachidonic Acid; D000255:Adenosine Triphosphate; D007986:Luteinizing Hormone; D005033:Ethylmaleimide; D002118:Calcium