Effects of Digoxin on Responsiveness to the Pressor Actions of Angiotensin and Norepinephrine in Man*

Abnormalities in sodium metabolism, including the presence of endogenous circulating digitalis-like sodium transport inhibitors, have been implicated in the genesis of essential hypertension. Digitalis has also been reported to affect adrenal steroid output in vitro. We studied the effects of 4 days of treatment with the digitalis glycoside digoxin upon blood pressure, the renin-aldosterone axis, and pressor and steroidogenic responses to graded norepinephrine, angiotensin, and ACTH infusions in six normal men after pretreatment with dexamethasone. Digoxin produced no significant changes in blood pressure, urinary electrolyte or aldosterone excretions, PRA or aldosterone concentrations, or the incremental responses of aldosterone or cortisol to angiotensin or ACTH. However, digoxin significantly augmented pressor responsiveness to both norepinephrine and angiotensin without significantly affecting the steady state baroreceptor-heart rate reflex. These findings support the hypothesis that digitalis-like factors may have important effects upon arterial blood pressure control in man.