Glyceraldehyde-3-phosphate dehydrogenase varies with age in glycolytic muscles of rats

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA, protein, and enzyme activity levels in hindlimb muscles of adult and senescent Fischer 344 x Br own Norway rats were investigated. Soleus muscles From adult and senescent rats had similar levels of GAPDH. In contrast, muscles containing a large p roportion of glycolytic fibers had lower GAPDH levels in senescent rats rel ative to these muscles in adult rats; this was observed at both the mRNA an d protein levels. These data indicate that skeletal muscle glycolytic capac ity of fast muscles is diminished with age and that it may he caused by cha nges at the level of transcription. Also, because GAPDH mRNA levels change with age in several rat muscles, GAPDH mRNA is not always a proper internal control for mRNA analyses of aging skeletal muscle.