Effect of 6-dehydro-DOCA and 6-dehydro-9 alpha-fluorocortisol acetate on the excretion of sodium and potassium in the rat.

Deoxycorticosterone acetate (DOCA) and 9 alpha-fluorocortisol acetate (9 alpha-F-Cac) can be modified by the introduction of a double bond at carbons 6 and 7 (6-dehydro-derivatives). Such a modification markedly changes the effect of the steroids on urinary excretion of Na+ and K+. Since 6-7 reduction of DOCA and 9 alpha-F-Cac substantially reduces affinity for Type II receptors but not Type I receptors, 6-dehydro-derivatives will thus bind preferentially to receptors influencing the retention of sodium (the "mineralocorticoid" or Type I receptor), and compete with mineralocorticoids for such receptors. We interpret the increase in both natriuresis and kaliuresis when mineralocorticoids and their dehydro-derivatives are administered together as evidence for a Type II receptor mediation of these ion fluxes.