The effect of prednisone on plasma norepinephrine concentration and renin activity in salt-depleted man.

Abstract

Abstract Restriction of sodium to 10 mEq. per day in normal man was followed by an increase in plasma norepinephrine concentration and increased urinary excretion of conjugated norepinephrine. These increases were associated with a decline in plasma volume. The correlation between increment of plasma norepinephrine concentration and plasma volume depletion was not large (R = −0.49), but the data do not exclude the possibility that plasma volume or a function of plasma volume was the stimulus resulting in elevation of plasma norepinephrine. Administration of prednisone was followed by decreases in plasma norepinephrine concentration and in urinary excretion of conjugated norepinephrine despite continued salt restriction and plasma volume depletion. Although the administration of prednisone was associated with a decline in plasma norepinephrine concentration, a similar decline was not observed in plasma renin activity. These results suggest that either sympathetic activity, as reflected by norepinephrine in plasma and urine, was not the stimulus to continued renin release in these subjects, or that prednisone sensitizes the renin-releasing mechanism to norepinephrine.