GROWTH-FACTORS AND PERICELLULAR COMPONENTS AS A LOCAL SIGNALING RELAYIN THE ACTION OF SYSTEMIC HORMONES

Recent years have shown that peptidic signals, originally identified a s growth factors, may represent a local signalling system involved in the regulation of cell function under the dependence of systemic hormo nes. As an example, (i) adrenocortical cells are highly sensitive to t ransforming growth factor-beta (TGF beta) which is a powerful inhibito r of their differentiated functions; (ii) adrenocortical cells produce and secrete TGF beta, which is present in the adrenal cortex in situ; (iii) adrenocorticotropin (ACTH), which is the best known positive ef fector of adrenocortical functions induces an up-regulation of TGF bet a receptors in adrenocortical cells. Altogether, these observations su ggest that TGF beta may be a local signalling system acting in balance with the systemic hormone ACTH to eventually tune the ability of adre nocortical cells to produce corticosteroids.