THE TIMING OF PROTEIN FEEDING AND DIETARY-PROTEIN LEVELS AFFECT TASTEPREFERENCE, SERUM ZINC CONCENTRATION AND GLOSSAL EPITHELIAL MORPHOLOGY IN GROWING RATS
R. Tabuchi et al., THE TIMING OF PROTEIN FEEDING AND DIETARY-PROTEIN LEVELS AFFECT TASTEPREFERENCE, SERUM ZINC CONCENTRATION AND GLOSSAL EPITHELIAL MORPHOLOGY IN GROWING RATS, Journal of the American College of Nutrition, 17(1), 1998, pp. 79-85
Objective: The present study investigated the effect of timing of prot
ein feeding on taste preference, serum zinc concentration and morpholo
gical changes of tongue epithelia. Methods: Weanling rats were fed one
of three diets: protein-free and 2.5 or 8% purified egg protein (PEP)
diets for 14 days (first feeding period). Rats in each group were fur
ther subdivided into there dietary treatments, totaling nine groups an
d fed one of the same three diets for 14 days (second feeding period).
Preference tests between 3 or 6 mmol/L NaCl vs. deionized water were
conducted in both feeding periods. At the end of each period, blood an
d tongue were collected for the measurement of serum zinc concentratio
ns and morphological observations. Results: The rats fed the protein-f
ree diet in the first feeding period did not discriminate 3 mmol/L NaC
l from deionized water in both feeding periods, even though adequate p
rotein was administered in the second feeding period. The rats fed the
2.5 or 8% PEP diet in the first feeding period discriminated 3 mmol/L
. NaCl from deionized water regardless of the protein levels in the di
et during the second feeding period. Serum zinc concentration was prop
ortionate to protein content in the diet at the end of each feeding pe
riod (p<0.0001), and low serum zinc concentration was restored by prot
ein feeding. Abnormal changes of tongue epithelia were observed only i
n the rats fed the protein-free diet throughout the two feeding period
s. Conclusions: The results suggest that protein nutrition immediately
after weaning is important to maintain normal taste function.