Effect of cerebellin on the pituitary-adrenocortical function in adult rats and the proliferative activity of immature and regenerating rat adrenal cortex

We have investigated the effects of cerebellin on the pituitary adrenal axi s and the proliferative activity of immature and regenerating adrenal corte x in the rat. The acute bolus administration of cerebellin did not alter AC TH plasma concentration, but at its higher dose (15 nmol/kg) the peptide en hanced the blood levels of both aldosterone and corticosterone. Three injec tions of cerebellin (10 nmol/kg) markedly increased the mitotic index (part s per thousand of metaphase-arrested cells) in the zona glomerulosa of imma ture rat adrenals. This treatment did not alter either aldosterone or corti costerone plasma concentrations in rats bearing regenerating adrenals, but did it decrease the proliferative activity at day 8 of adrenal regeneration . We conclude that cerebellin exerts its adrenocortical secretagogue and pr oliferogenic actions acting directly on the adrenal gland of adult and imma ture rats, independently of any effect on the pituitary ACTH release. The l ack of secretagogue effects and the clearcut antiproliferogenic action obse rved in rats with regenerating adrenals may be ascribed to the effects of c erebellin on the various mechanism involved in this process.