Autocrine role of TGFbeta1 in adrenal.

Three main criteria are required to postulate that a factor has an autocrine action in any cell: presence of receptors and biological effects of the factor; local production which must be regulated by physiological signals and the inhibition of its secretion or action should cause effects opposite to those caused by the exogenous factor. In adrenal cells, transforming growth factor beta1 (TGFbeta1) fulfilled these criteria: 1) Adrenal cells possess TGFbeta1 receptors and this factor regulates the expression of adrenal cell specific genes, including ACTH and angiotensin II (AngII) receptors and several steroidogenic enzymes, leading to changes in the steroidogenic responsiveness; 2) Adrenal cells express and secrete TGFbeta1 and its secretion is regulated by the two adrenal specific hormones ACTH and AngII; 3) The blockade of TGFbeta1 protein synthesis by an antisense oligonucleotide produces changes in adrenal cell functions opposed to those induced by the exogenous factor.