Dual Activation of Adenylate Cyclase and Phospholipase C by Prostaglandins of the E and I Series in Bovine Luteal Cells
Maintenance of the corpus luteum (CL) is dependent on a balance between a number of luteotropic and luteolytic factors (recently reviewed in references 1 and 2). Prostaglandins (PG) are important paracrine and endocrine factors which control CL function. Prostaglandins of the E and I series stimulate steroidogenesis in bovine luteal tissues (2–4), presumably via their ability to activate adenylate cyclase (4,5). Thus, their actions are analogous to the stimulatory actions of luteinizing hormone (LH) on adenylate cyclase and progesterone synthesis. Although PGF2α has a luteolytic effect in vivo, PGF2α also stimulates progesterone synthesis in incubations of cells (2) or slices (3,6) of bovine luteal tissue in vitro. This luteotropic action of PGF2α, however, does not involve the activation of adenylate cyclase (4) or an increase in cAMP (4,7) in bovine luteal tissue. Instead, PGF22α stimulates the inositol phospholipid-phospholipase C transmembrane signalling system (7–10). This system is coupled to increases in intracellular calcium and protein kinase C activation (8,10,11). Recent studies also show that LH activates the inositol phospholipid-phospholipase C signalling system in bovine luteal cells (12,13). The present studies were performed to examine whether the luteotropic prostaglandins of the E and I series also activate this transmembrane signalling system.
KeywordsLuteinizing Honnone Corpus Luteum Inositol Phosphate Luteal Cell Inositol Trisphosphate
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