Hypertensive potency of 18-oxocortisol in the rat

The hypertensogenic effect of 18-oxocortisol, an aldosterone analogue possessing both mineralocorticoid and glucocorticoid properties, was studied at the same dosage but under different experimental conditions in two experiments. Under experimental conditions conducive to the development of mineralocorticoid hypertension (i.e., rats with a single kidney on a high NaCl intake), there was an extremely rapid onset of saline polydipsia and hypertension accompanied by cardiac and renal enlargement, marked thymic involution without adrenal atrophy, cardiovascular lesions, and hypokalemia. With the exception of the thymic changes, the same changes occurred in rats given the biologically equivalent dose of deoxycorticosterone acetate. Under circumstances favoring the development of glucocorticoid hypertension (i.e., intact rats on a normal sodium intake), the same dose had only a transient blood pressure-elevating effect, attaining prehypertensive levels at most, and caused neither chronic hypertension nor hypokalemia. The biologically equivalent glucocorticoid dosage of cortisol was similarly ineffective. Under these circumstances, both steroids caused thymus involution but only 18-oxocortisol caused kidney enlargement.