Mineralocorticoid like effect of new 18-hydroxy-steroid isolated from urine of hypertensive patients.

The affinity of new urinary 18-hydroxy-steroid (Cp x) for mineralocorticoid receptors was estimated. When rat kidney slices were incubated with 2 x 10(-9) M 3H-aldosterone, Cp x (2 x 10(-5) M) was able to compete with aldosterone for the mineralocorticoid cytosol receptors. Cp x had low but significant affinity for mineralocorticoid receptor sites. This affinity was less than that obtained with 18-OH-progesterone. Moreover, in the adrenalectomized rats, the injection of Cp x induced a decrease of urinary Na+/K+ ratio which seems comparable to that obtained with 18-OH-progesterone.