Effect of polaprezinc on taste disorders in zinc-deficient rats

The effect of polaprezinc, a chelate compound consisting of zinc ion and L-carnosine, on abnormalities of taste sensation induced by feeding a zinc-deficient diet to rats was examined by using the two-bottle preference test (quinine hydrochloride as a bitter taste and sodium chloride as a salty taste). Rats were fed either a zinc-deficient or a zinc-sufficient diet. The zinc-deficient diet increased the preference for both taste solutions, while polaprezinc (at doses of 3 and 10 mg/kg) restored the altered taste preferences. We also evaluated the proliferation of taste bud cells using 5-bromo-2′-deoxyuridine (BrdU). The BrdU incorporation into taste bud cells was significantly reduced in rats fed a zinc-deficient diet compared with rats fed a zinc-sufficient diet (from 50.8% to 45.0%, p < 0.05) and this reduction was reversed by polaprezinc at doses of 1, 3, and 10 mg/kg, increasing to 50.2%, 53.5%, and 52.5%, respectively. These findings indicate that zinc deficiency induces the delayed of proliferation of taste bud cells, while polaprezinc improves cell proliferation. In conclusion, polaprezinc had a therapeutic effect in a rat model of abnormal taste sensation. Its mechanism of action was suggested to involve improvement of the decrease in taste bud cell proliferation caused by zinc deficiency.