The proposed studies are designed to evaluate the hypothesis that adrenocortical dysfunction related to altered synthesis or control of key steroidogenic enzymes can lead to increased secretion of hypertensinogenic steroids from the adrenal. The major focus initially will be on the pathogenesis of androgen-induced hypertension where our previous studies have revealed that there are selective effects of androgens on cytochrome P-450-11 beta activity of the adrenocortical inner zones. The mechanism of this will be studied by measuring steroidogenic enzyme gene expression from control and androgen-treated rats. Specific antibodies will be used to quantitate cytochrome P-450-11 beta as well as P-450scc, adrenodoxin, P-450-21 and NADPH-cytochrome P-450 reductase using immunoisolation techniques. cDNA's against P-450-11 beta, P-450scc and P-450-21 will be used to quantitate mRNA's encoding for these enzymes. In view of potential effects of androgen on the secretion of proopiomelanocortin (POMC)-derived peptides, these studies will be extended to adrenocortical cells in primary culture. Also, we will measure the effect of androgens on circulating and pituitary levels of POMC-derived peptides as well as direct effects of androgens on pituitary cell cultures. In related studies we examine the gene expression of key adrenal steroidogenic enzymes in regenerating adrenals in order to understand more fully how altered levels of these enzymes is related to increased biosynthesis of mineralocorticoids. Spontaneously hypertensive rats (SHR) will also be studied in the prehypertensive and hypertensive state in order to identify potential abnormalities in adrenal and pituitary hormone biosynthesis. Our work with POMC-derived peptides will emphasize pro-gamma-MSH's shown by us to synergize with ACTH in stimulating aldosterone and glucocorticoid secretion. We will study the mechanism of action of pro-gamma-MSH's in normal rat adrenal zona glomerulosa tissue and also in human aldosteronoma cells. These studies have the potential for enhancing our understanding of the altered control of aldosterone production in aldosterone-secreting adenomas as well as the role in normal glomerulosa and aldosteronoma cells of a hormone- and cAMP-responsive steroidogenesis activator polypeptide (SAP), recently isolated and characterized by us.
