Adrenergic Nervous System in Sodium Metabolism: Effects of Guanethidine and Sodium-retaining Steroids in Normal Man*

Abstract

The response to rapid infusion of physiologic saline (2 L in 120 minutes) and the response to Na retaining steroids and large quantities of dietary Na (250 mEq/day) were studied in normal subjects before and after adrenergic blockade with guanethidine. Na excretion during infusion of saline was 50 to 300% greater after adrenergic blockade and was associated with a higher clearance of inulin. During treatment with steroid (deoxy-corticosterone acetate, 20 mg/day, or 2-methyl-9[alpha]-fluorohydrocortisone, 0.5 mg/day) Na retention and weight gain were less after blockade, 214 to 566 mEq and 0.36 to 2.25 kg, as opposed to 722 to 1,069 mEq and 3.09 to 4.67 kg. The much smaller quantities of Na retained with guanethidine and steroid were associated with losses of K that equaled or exceeded those observed throughout the longer period of Na retention with steroid alone. This increase in excretion of Na and K with guanethidine was not dependent on a higher glomerular filtration rate. The adrenergic nervous system appears to play an important role in Na metabolism in normal man, probably through an effect on the renal vasculature.