title: Protein kinase C and Gi-protein mediated modulation of cAMP production in different stages of the rat seminiferous epithelium.
abstract: The modulatory role of protein kinase C (PK-C)- and Gi-protein-mediated signal transduction systems was studied in the cyclic variation of follicle-stimulating hormone (FSH)-stimulated cAMP production of rat seminiferous tubules. FSH (Metrodin, Serono, 30 mg/l) stimulated cAMP production 10-fold (p less than 0.01) in a 3 h incubation of 5 mm segments of seminiferous tubules of stages II-VI of the epithelial cycle, but only 2-fold (p less than 0.01) in stages VII-VIII. The PK-C activator 12-O-tetradecanoylphorbol 13-acetate (TPA, 100 nmol/l) suppressed the FSH effect on cAMP output by 50-70% (p less than 0.01) in stages II-VI, but had no effect in stages VII-VIII. If the tubular segments were preincubated for 3 h in the presence of pertussis toxin (PT, 100 micrograms/l), the FSH-stimulated cAMP production of stages VII-VIII increased by 100-200% (p less than 0.01), and now they also became responsive to the TPA suppression. Conversely, no effect of PT was observed in stages II-VI. Cholera toxin (CT, 100 micrograms/l) and forskolin (Fk, 100 mumol/l) nearly similarly stimulated the cAMP production in both stages studied (about 10-fold, p less than 0.01), and TPA and PT potentiated the effects in a non-additive fashion. In conclusion, both Gi-protein and PK-C-mediated mechanisms modulate cAMP production of rat seminiferous tubules. A clear cyclic variation can only be demonstrated in FSH-stimulated cAMP production, but not if the Gs-protein or adenylate cyclase are directly stimulated.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physiology, University of Turku, Finland.
authors.forename: H
authors.initials: H
authors.lastname: Nikula
authors.forename: K
authors.initials: K
authors.lastname: Vihko
authors.forename: I
authors.initials: I
authors.lastname: Huhtaniemi
mesh_terms: D037361:Adenylate Cyclase Toxin; D000818:Animals; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis*; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008297:Male; D037342:Pertussis Toxin; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012670:Seminiferous Epithelium / Q000378:metabolism*; D015398:Signal Transduction; D013737:Testis / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D037361:Adenylate Cyclase Toxin; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D005640:Follicle Stimulating Hormone; D002772:Cholera Toxin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate