Zinc deficiency and taste dysfunction; contribution of carbonic anhydrase, a zinc-metalloenzyme, to normal taste sensation.

The present study was designed to clarify the effect of zinc deficiency on sodium chloride preference, the lingual trigeminal and taste nerves transduction, and carbonic anhydrase (CA) activity of the tongue surface and salivary gland. Male SD rats, 4 weeks old, were divided into four groups, and fed zinc-deficient (Zn-Def), low-zinc (Low-Zn), and zinc-sufficient diets with free access (Zn-Suf) and pair-feeding (Pair-fed). After taking part in the preference tests for 42 days, the rats were provided for the chorda tympani and lingual trigeminal nerves recordings, then finally sacrificed and the tongue and submandibular gland excised to measure CA activity. Sodium chloride preference increased only after 4 days of the feeding of zinc-deficient and low-zinc diets, which means that the taste abnormality appears abruptly in zinc deficieny and even though in marginal zinc deficiency. Reduced CA activities of the taste-related tissues in zinc-deficient group paralleled well with the decreased taste and lingual trigeminal nerves sensitivities.