Dietary zinc deficiency decreases glutathione S-transferase expression in the rat olfactory epithelium

Zinc deficiency leads to olfactory and gustatory dysfunction, but little is known about the underlying molecular mechanism of this phenomenon. We exam ined the effect of dietary zinc deficiency on the rat olfactory epithelium. Immunoreactivities of glutathione S-transferase (GST) mu, neuron-specific enolase (NSE) and proliferating cell nuclear antigen (PCNA), and in situ hy bridization of GST mu mRNA in the olfactory epithelia were examined under d ifferent dietary zinc intake conditions. Adult male rats were fed a zinc-de ficient (ZD) diet (0.5 mg zinc/kg diet), whereas control rats, including pa ir-fed (PF) and zinc-adequate (ad libitum consumption, AL) groups, were fed a zinc-adequate diet (58 mg zinc/kg diet) for 7 wk. We also examined the e ffect of zinc replacement (ZR) by subsequently feeding half of the ZD group a zinc-adequate diet for 5 wk after the initial 7-wk deprivation. No signi ficant differences in immunoreactivity for NSE in olfactory epithelial rece ptor cells or for PCNA in basal cells were noted among groups. Intense GST mu immunoreactivity and hybridization signals were observed in olfactory su pporting cells of AL, PF and ZR groups, but very minimal or no such signal was noted in ZD rats. Our findings indicated that zinc deficiency reduces G ST mu expression in the supporting cells of rat olfactory epithelia but doe s not affect receptor cell proliferation or maintenance.