title: LH-dependent steroid production and protein phosphorylation in culture of rat tumour Leydig cells.
abstract: The possible cause of the decreased responsiveness of cultured Leydig cells to stimulation with LH was investigated with rat tumour Leydig cells cultured at 32 degrees C for 2 days. Pregnenolone production and phosphorylation of proteins were studied in combination with the activity of cyclic AMP-dependent protein kinase. Pregnenolone production in cultured tumour Leydig cells decreased from 45 +/- 16 on day 0 to 14 +/- 7 on day 2 (ng/60 min/mg protein) under basal conditions and from 226 +/- 108 on day 0 to 30 +/- 24 on day 2 (ng/60 min/ng protein) under LH-stimulated conditions (means +/- SD, n = 4). This decrease may be accounted for by decreased capacity of cholesterol side-chain cleavage which decreased (in the presence of 25-hydroxycholesterol) from 1.68 +/- 0.26 on day 0 to 0.74 +/- 0.48 on day 2 (microgram/60 min/mg protein; mean +/- SD, n = 4) and decreased activity of cyclic AMP-dependent protein kinase (as apparent from a direct assay of protein kinase activity and the extent of phosphorylation of LH-dependent phosphoproteins).
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002460:Cell Line; D006888:Hydroxycholesterols / Q000494:pharmacology; D007984:Leydig Cell Tumor / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000494:pharmacology*; D008970:Molecular Weight; D010750:Phosphoproteins / Q000378:metabolism*; D011284:Pregnenolone / Q000096:biosynthesis*; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats
chemical_list: D006888:Hydroxycholesterols; D010750:Phosphoproteins; D003994:Bucladesine; D011284:Pregnenolone; C007997:25-hydroxycholesterol; D007986:Luteinizing Hormone; D011494:Protein Kinases; D015056:1-Methyl-3-isobutylxanthine