Enhancement of glial cell line-derived neurotrophic factor expression in rat adrenal glands by toluene exposure

Toluene, a widely used industrial organic solvent, has been shown to influe nce the function of catecholaminergic cells including sympathoadrenergic ne urons and adrenal medullary cells. While glial cell line-derived neurotroph ic factor (GDNF), a member of the transforming growth factor-beta superfami ly, has recently been shown to be expressed in rat adrenal glands, and sugg ested as playing a potential autocrine or paracrine role in development and differentiation of the adrenal medullary cell. Based on these findings, it seemed of interest to examine the effect of toluene exposure on GDNF expre ssion in the adrenal medulla. Toluene inhalation (1500 ppm for 4 h on 4-10 days) increased GDNF protein content in rat adrenal glands without any sign ificant change in GDNF mRNA level. Furthermore, toluene exposure failed to cause any notable change in the expression of mRNA encoding phenylethanolam ine N-methyltransferase (PNMT), a stress-inducible enzyme in the adrenal me dulla. These results suggest that the elevation of GDNF protein expression caused by toluene exposure is likely due to the enhancement of protein synt hesis and/or processing rather than the stimulation of GDNF gene transcript ion in rat adrenal glands, and may not be directly associated with the stre ss response of adrenal glands during toluene inhalation.