Sodium deprivation during thiamin deficiency in rats: hormonal, histological, and behavioral responses.

Adrenal function, determined by adrenocortical hormone measurement and histological studies, was examined in adult rats fed on of the following four diets for four weeks: thiamin-sufficient, sodium-adequate (+B/+Na) or inadequate (+B/-Na); and thiamin-deficient, sodium-adequate (-B/+NA) or inadequate (-B/-Na). Thiamin-deficiency significantly depressed plasma and urinary aldosterone responses to sodium deprivation; on the other hand, thiamin status had no consistent significant effect on aldosterone levels in sodium-adequate rats. Plasma corticosterone levels were significantly elevated by thiamin deficiency and yet unaffected by sodium deprivation. Histological examination of the adrenal glands in thiamin-deficient rats revealed a suboptimal zona glomerulosa response to sodium deprivation. Juxtaglomerular granulation in the kidneys indicated that renin secretion was adequate in thiamin-deficient rats. In another experiment, salt (NaCl) appetite development was confirmed in adult rats fed the -B/+Na diet. A direct role of aldosterone in producing salt appetite in thiamin-deficient rats seems unlikely since aldosterone levels were essentially unchanged in rats fed the -B/+Na diet. Instead, the elevated corticosterone levels in thiamin-deficient rats suggest a general stress mechanism for salt appetite development of which the reduced aldosterone response to sodium deprivation is a symptom.