EXPRESSION AND REGULATION OF G-ALPHA-Q AND G-ALPHA-11 MESSENGER-RNAS AND PROTEINS IN BOVINE ADRENAL CELLS

Bovine adrenal cortical cells (BAC) express corticotropin (ACTH) and a ngiotensin II (AngII) receptors (AT1 subtype), which are coupled to ad enylate cyclase and phosphoinositide pathways, respectively. The coupl ing of AT1 to phosphoinositide breakdown is mainly pertussis toxin-ins ensitive suggesting that this receptor is coupled to Gaeq/Gae11. In th e present work we have demonstrated that BAC express G alpha g and G a lpha 11 mRNA and proteins, and their variation during culture as well as their regulation by ACTH and AngII is different. ACTH enhanced G al pha q mRNA levels mainly by increasing the transcription rate. In addi tion, ACTH increased both G alpha q and G alpha 11 proteins without ch anging their half-lives. In contrast, AngII reduced both G alpha q mRN A and protein and increased G alpha 11 mRNA but not G alpha 11 protein . The decrease of Gag mRNA levels was mainly due to a marked reduction of its half-life. These changes in G alpha q/G alpha 11 proteins indu ced by both hormones were associated with an enhanced AngII-induced in ositol phosphate accumulation, more marked after stimulation with ACTH than after AngII pretreatment. In summary, the present results demons trated that BAC express both G alpha q and G alpha 11 and their regula tions are different and in contrast to other cell types these regulati ons do not involve changes in the half-life of G alpha q/G alpha 11 pr oteins.