PREFERENCE FOR SODIUM-CHLORIDE IS REDUCED IN PROTEIN-DEPRIVED JUVENILE RATS

The influence of dietary protein levels on the preference for sodium c hloride was studied in juvenile rats fed diets containing 0, 25 or 50 g purified egg protein/kg and 20.0 mg zinc/kg diet. Preference tests b etween aqueous solution of NaCl (2-51 mmol/L) or deionized water were conducted. Blood samples were collected for measuring the serum zinc c oncentration. Scanning electron microscopy was performed to observe th e rats' tongue epithelia. Only the rats fed 50 g purified egg protein/ kg diet preferred the lowest concentration of 2 mmol/L NaCl solution t o deionized water, whereas the rats fed protein-free diet did not disc riminate diluted NaCl solution until the concentration was 9 mmol/L. T he filiform papillae of the protein-free diet fed group showed signifi cantly less development than the 25 g purified egg protein/kg and the 50 g purified egg protein/kg diet-fed groups. The more protein the die ts contained, the higher was the serum concentration of zinc. Signific ant correlations were observed between protein intake and discriminate d NaCl concentration (r = -0.93, P < 0.001), serum zinc (r = 0.90, P < 0.001) or length of filiform papillae (r = 0.93, P < 0.001). The pres ent study suggests that taste preference is impaired by protein malnut rition and this may be related to zinc status.