THE EFFECT OF ADRENAL ARTERIAL INFUSION OF HYPERTONIC NaHCO3 SOLUTION ON ALDOSTERONE SECRETION IN SODIUM DEFICIENT SHEEP

Abstract

Conscious trained sheep with adrenal autotransplants were allowed to become severely Na⁺ deficient by uncompensated salivary loss via a unilateral permanent parotid fistula. Hypertonic NaHCO₃ was infused into the adrenal artery at concentrations and rates appropriate to locally change adrenal plasma (Na⁺), (K⁺) and (HCO₃⁻) to Na⁺ replete levels without significant alteration of body Na⁺ status, or systemic ionic concentrations. After 2 hours of infusion aldosterone secretion rate was not significantly decreased; after 4–6 hours of infusion aldosterone secretion rate was significantly reduced but remained at levels appropriate for moderate to severe Na⁺ deficiency. The direct adrenal action of plasma ionic changes then, fails to explain the fall in secretion rate to close to Na replete levels which is seen over 2–6 hours after an animal rapidly corrects body Na⁺ deficit by drinking 2–3 1 of hypertonic NaHCO₃ solution (300 mEq./l) – since the adrenal arterial infusion produced the same ionic changes as occur systemically after drinking adequate NaHCO₃ to correct body Na⁺ deficit.