title: Steroidogenic enzyme activity after acute activation of protein kinase (PK) A and PKC in ovine small and large luteal cells.
abstract: Intracellular effector systems which utilize PKA and PKC can be pharmacologically activated by forskolin and phorbol 12-myristate 13-acetate (PMA) and appear to be important for regulation of steroidogenesis by cells of the corpus luteum. In this study the effect of pharmacologic activation of PKA (forskolin) or PKC (PMA) on the activity of adenylate cyclase, cholesterol esterase, P450 cholesterol side chain cleavage (P450scc) and 3 beta-hydroxysteroid dehydrogenase/delta 5, delta 4 isomerase (3 beta HSD) was determined. Basal adenylate cyclase activity (as measured by intracellular and secreted cAMP) was extremely low in both large and small luteal cells. Forskolin stimulated adenylate cyclase activity in both large and small luteal cells but progesterone production was increased only in small cells. PMA inhibited progesterone production by large and forskolin-stimulated small cells without altering adenylate cyclase activity. Basal cholesterol esterase activity was greater in small than in large cells and was stimulated by forskolin only in small cells. PMA did not significantly alter cholesterol esterase activity in either cell type. Activity of P450scc or 3 beta HSD was measured by conversion of hydroxylated cholesterol derivatives (P450scc) or pregnenolone (3 beta HSD) to progesterone. Although basal progesterone production was 47 times greater in large than small cells, there was only 5.1 (P450scc) and 6.4 (3 beta HSD) times greater enzyme activity in large than in small luteal cells. Activation of PKA and/or PKC did not alter the activity of P450scc or 3 beta HSD in either cell type.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physiology, Colorado State University, Fort Collins.
authors.forename: M C
authors.initials: MC
authors.lastname: Wiltbank
authors.forename: C J
authors.initials: CJ
authors.lastname: Belfiore
authors.forename: G D
authors.initials: GD
authors.lastname: Niswender
mesh_terms: D015096:3-Hydroxysteroid Dehydrogenases / Q000235:genetics; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D048429:Cell Size; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D003338:Corpus Luteum / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D008075:Lipoproteins, HDL / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000494:pharmacology; D011374:Progesterone / Q000096:biosynthesis*; D011493:Protein Kinase C / Q000378:metabolism*; D012756:Sheep; D002787:Sterol Esterase / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D008075:Lipoproteins, HDL; D005576:Colforsin; D011374:Progesterone; D007986:Luteinizing Hormone; D015096:3-Hydroxysteroid Dehydrogenases; D002786:Cholesterol Side-Chain Cleavage Enzyme; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D002787:Sterol Esterase; D000262:Adenylyl Cyclases; D013755:Tetradecanoylphorbol Acetate