A histochemical study of APUD ability in the taste buds of experimentally induced zinc-deficient mice

To explore the relationship between taste acuity and zinc deficiency, a histochemical investigation was made into the taste buds of mice fed a zinc-deficient diet. Nine weeks after the start of the diet, the average serum zinc level of the mice was 45% lower than that of a control group of mice. Moreover, growth was arrested significantly. Two-bottle preference tests revealed that the intake ratio of 10(-5) M quinine hydrochloride solutions had increased markedly in the zinc-deficient mice compared with the controls. The circumvallate taste buds showed no morphological changes. Fluorescent histochemical examination showed an uptake of a monoamine precursor (5-HTP) by the gustatory cells in the zinc-deficient mice after the 5-HTP treatment. Upon immunohistological examination, however, no serotonin immunoreactivity appeared in the gustatory cells of the zinc-deficient mice after the 5-HTP treatment. These results suggest that zinc-deficiency may induce hypogeusia and decrease the ability to transform a monoamine precursor to monoamine in the gustatory cells, albeit the monoamine precursor uptake ability is not affected.