Proliferative and nutritional dependent regulation of glyceraldehyde‐3‐phosphate dehydrogenase expression in the rat liver

. Glyceraldehyde‐3‐phosphate dehydrogenase is a multifunctional protein possessing numerous cytoplasmic and nuclear functions associated with cellular proliferation. Despite the emerging role of glyceraldehyde‐3‐phosphate dehydrogenase in regulating the proliferative process, there is a paucity of data regarding its expression and intracellular distribution in non‐malignant proliferating hepatocytes. Thus the aim of the present study was to document the intracellular distribution of glyceraldehyde‐3‐phosphate dehydrogenase protein in proliferating hepatocytes derived from regenerating rat livers, and glyceraldehyde‐3‐phosphate dehydrogenase gene expression in fasted and re‐fed rats following partial hepatectomy (PHx). Glyceraldehyde‐3‐phosphate dehydrogenase mRNA and protein expression were documented by Northern and Western blot analyses, respectively, at various times following 70% PHx in adult Sprague–Dawley rats. At 24 h post‐surgery, glyceraldehyde‐3‐phosphate dehydrogenase mRNA expression was significantly increased in both PHx and sham operated rats ( P  < 0.001), respectively. Despite the increase in glyceraldehyde‐3‐phosphate dehydrogenase mRNA expression in both groups, only PHx rats had a significant increase in the nuclear fraction of glyceraldehyde‐3‐phosphate dehydrogenase protein (threefold increase compared to sham and baseline levels, P  < 0.01), cytoplasmic levels of glyceraldehyde‐3‐phosphate dehydrogenase protein remained unaltered in both groups. In terms of the effects of feeding and fasting on rats there were no significant differences in glyceraldehyde‐3‐phosphate dehydrogenase mRNA levels, whether fasted or refed, in rats that had undergone PHx, 8 h earlier. On the other hand, glyceraldehyde‐3‐phosphate dehydrogenase mRNA levels were significantly increased in refed compared to fasted sham operated rats 8 h following surgery. Serum insulin concentrations were higher in the refed PHx and sham groups compared to their fasted counterparts. The results of this study indicate that although glyceraldehyde‐3‐phosphate dehydrogenase mRNA are altered to the same extent in PHx and sham‐operated rats following surgery, increases in the nuclear fraction of glyceraldehyde‐3‐phosphate dehydrogenase protein only occur in PHx rats. The results also indicate that glyceraldehyde‐3‐phosphate dehydrogenase expression is affected by the nutritional status of animals undergoing abdominal sham surgery.