Inhibition by staurosporine of TRH-induced refractoriness of inositol phospholipid hydrolysis in rat anterior pituitaries.
To clarify the mechanism(s) underlying the TRH-induced refractory state of the anterior pituitary, we evaluated rat pituitary inositol phospholipid hydrolysis in the presence of staurosporine. TRH caused a time- and dose-dependent accumulation of inositol phosphates in rat anterior pituitary slices. Pretreatment with 550 nmol TRH/l completely abolished the subsequent accumulation of inositol phosphates in response to 140 nmol TRH/l. TRH-stimulated accumulation of inositol phosphates did not occur after pretreatment with 0.2 mumol phorbol ester/l. Refractoriness of inositol phospholipid hydrolysis which was produced by pretreatment with TRH and phorbol ester was inhibited by staurosporine. The present data support the hypothesis that protein kinase C plays a profound role in TRH induction of the refractory state of inositol phospholipid hydrolysis in the anterior pituitary.
Iriuchijima
T
T
First Department of Internal Medicine, Gunma University, School of Medicine, Maebashi, Japan.
Mori
M
M
D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D006868:Hydrolysis / Q000187:drug effects; D007295:Inositol Phosphates / Q000378:metabolism*; D008297:Male; D010703:Phorbol Esters / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D051381:Rats; D011919:Rats, Inbred Strains; D019311:Staurosporine; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D000470:Alkaloids; D007295:Inositol Phosphates; D010703:Phorbol Esters; D013973:Thyrotropin-Releasing Hormone; D011493:Protein Kinase C; D019311:Staurosporine