Changes in Axonally Transported Proteins in the Rat Visual System Following Systemic Methyl Mercury Exposure

Abstract

In an effort to understand the effect of methylmercury on protein synthesis and axonal transport, we have analysed the composition and rate of axonally transported proteins in the retinal ganglion cells of the mature rat. By means of scintillation spectrometry and autoradiography, it was established that systemic exposure to 4 mg Hg/kg/day for four to six days, or twelve days, resulted in an increased rate and volume of transported protein-bound radioactivity in the visual system of the mature rat. In an effort to characterize these changes, the composition of transported polypeptides was analysed by means of SDS polyacrylamide gel electrophoresis. Selective changes in the composition of transported polypeptides were evident. These changes of a small subset of proteins known as GAPs (growth-associated proteins) are consistent with the suggestion that they may have been involved in growth-specific functions during the early stages of methyl mercury exposure. We concluded that, during this period, retinal ganglion cells may express growth-related genes and engage in regenerative processes.