Zinc nutrition and salt preference in rats

Zinc-deficient rats have an increased preference for sodium chloride (saltwater). We investigated the possibility that this elevated saltwater preference is due to nonfunctional taste receptors. In experiment I, zinc-deficient rats consumed more saltwater than zinc-sufficient rats at most sodium chloride concentrations tested (0.001-1.0 M). When the zinc-deficient rats were fed a zinc-sufficient diet, the clinical symptoms of zinc deficiency rapidly disappeared. However, the rats still preferred saltwater to a greater extent than rats maintained on the zinc-sufficient diet. In experiment II, rats fed diets supplemented with levels of zinc below the requirement for maximum growth had an increased preference for saltwater (0.15 M NaCl). In experiment III, electrophysiological responses of the taste nerves to various concentrations of sodium chloride, sucrose, quinine . HCl, and hydrochloric acid were the same in both zinc-deficient and zinc-sufficient rats. We conclude that the taste receptor sensitivity of the rat is not impaired by zinc deficiency. The increased salt preference of zinc-deficient rats might be related to some endocrine or central nervous system disorder precipitated by inadequate dietary zinc.