Decreased stimulation of adenylate cyclase by growth hormone-releasing factor in the anterior pituitary of old rats.

摘要: Adenylate cyclase activity was studied in anterior pituitary homogenates from young adult (6 months) and old (20 24 male rats. Basal, NaF-, GTP-, 5'-guanylimidodiphosphate (Gpp(NH)p)- forskolin-stimulated activities were similar the three groups, implying that stimulatory guanyl nucleotide regulatory binding site (NS) catalytical unit unaffected by aging. Vasoactive intestinal peptide (VIP)-stimulated adenylate also identical groups. The efficacy (i.e., maximum effect) of growth hormone-releasing factor [GRF(1-29)-NH2] on reduced 45-49% senescent rats with no change potency concentration required for half-maximal enzyme stimulation). These results suggest aging induced a selective loss functional GRF receptors but influenced neither coupling between receptors, NS catalytic nor per se.