New mineralocorticoids: 5alpha-dihydroaldosterone and 5alpha-dihydro-11-deoxycorticosterone

Mineralocorticoid activity of several delta4-3-ketosteroids and their 5alpha-dihydro analogs were evaluated by bioassay using urinary Na:K ratio of adrenalectomized rats as an index of mineralocorticoid activity. Among delta4-3-ketosteroids, aldosterone, 11-deoxycorticosterone, corticosterone, cortisol, 11-dehydrocorticosterone, and cortisone showed mineralcorticoid activity with aldosterone, the most potent of the series, showing virtually maximum activity at a dose of 0.25 microgram/rat. 5alpha-Dihydroaldosterone and 5alpha-dihydro-11-deoxycorticosterone possessed distinct mineralcorticoid activity, albeit less than aldosterone and 11-deoxycorticosterone. 5alpha-Dihydrocorticosterone, 5alpha-dihydrocortisol, 5alpha-dihydro-11-dehydrocorticosterone, and 5alpha-dihydrocortisone did not show mineralocorticoid activity in doses up to 100 microgram/rat. It is concluded that reduction of the 4.5 double bond diminishes mineralocorticoid activity of delta4-3-ketosteroids. Nevertheless, 5alpha-dihydroaldosterone has distinct mineralocorticoid activity with potency of 1.8% of that of aldosterone and approximately the same as that of 11-deoxycorticosterone.