The objective of this research is to investigate the relationship between various forms of hypertension in the rat and mineralocorticoid (aldosterone) receptors located in smooth muscle cells and fibroblasts grown from the rat aorta. The receptors may be involved in the accumulation of water and electrolytes which occurs in the cells of the artery wall during the development of hypertension. This accumulation of water and electrolytes causes the cells to swell. The swelling narrows the lumen of the vessel, stiffens the vessel and increases the peripheral resistance. Initially, the capacity, specificity and affinity of the receptors will be furter characterized by Sephadex G 150 and ion exchange chromatography and temperature and a pH stability. These corticoid aortic receptors will be compared in cells from strains of rats which are resistant or susceptible to different types of hypertension. The quantity of these corticoid receptors will be compared to the fluid and electrolyte content of an aorta similar to that from which the cultured cells were derived. Elucidation of the relationship between hypertension in the rat and aortic mineralocorticoid receptors may lead to an increased understanding of hypertension in both rat and man.