Polaprezinc, a zinc compound, is distributed to the lingual epithelium and increases its zinc concentration in zinc-deficient rats

AimsTo clarify the mechanism underlying the effect of polaprezinc on hypogeusia, we investigated the uptake of polaprezinc by the tongue in rats.Main methodsRats were fed a zinc-sufficient (Zn(+)) or zinc-deficient (Zn(−)) diet. After 4 weeks on the Zn(−) diet, polaprezinc (1, 3, or 10 mg/kg) or [65Zn] polaprezinc (10 mg/kg) was administered orally once a day. The zinc concentration or the 65Zn radioactivity of the tongue was measured by inductively-coupled plasma mass spectrometry or gamma counting, respectively. In addition, the distribution of 65Zn in the tongue was analyzed by microautoradiography and the proliferative activity of taste bud cells was measured from the uptake of 5-bromo-2′-deoxyuridine.Key findingsThe zinc concentration of the lingual epithelium, but not the whole tongue, was markedly decreased in Zn(−) rats compared with Zn(+) rats. After administration of polaprezinc to Zn(−) rats at doses of 1, 3, and 10 mg/kg, the zinc concentration in the lingual epithelium increased significantly from 85 ± 4 to 105 ± 7 (p < 0.05), 120 ± 3 (p < 0.001), and 124 ± 3 (p < 0.001) µg/g, respectively. After administration of [65Zn] polaprezinc, the 65Zn radioactivity of the tongue and serum were higher in Zn(−) rats than in Zn(+) rats. 65Zn was mainly detected in the epithelium on microautoradiograms of the tongue in Zn(−) rats. In addition, polaprezinc (3 and 10 mg/kg) improved the reduced proliferation of taste bud cells due to zinc deficiency.SignificancePolaprezinc is distributed to the lingual epithelium and restores its zinc concentration in Zn(−) rats resulting in improvement of cellular functions, especially proliferation.