ACTH-elicited sodium appetite in sheep

Intramuscular injections of long-acting synthetic ACTH (45 U twice daily for 5 days) caused a large increase in the intake of 0.5 M NaCl in sheep. Mean Na intake of the sheep on the last 3 days of treatment approximated 50% of their total extracellular fluid Na. The mineral appetite was specific for NaCl. Intakes of 0.5 M KCl or 0.25 M CaCl2 were not significantly altered. The enhanced appetite for Na induced by ACTH appeared to precede any increase in urinary Na excretion. ACTH treatment was ineffective in adrenalectomized sheep. However, an infusion into adrenalectomized sheep of a combination of adrenal steroid hormones (including aldosterone, deoxycorticosterone, 11-deoxycortisol, cortisol, and corticosterone) that contrived blood levels similar to those, obtained with ACTH treatment in normal sheep did induce Na appetite. Thus, ACTH induces a specific, adrenal-steroid hormone-dependent Na appetite in sheep.