LACTIC ACID DEHYDROGENASE ISOENZYMES OF RAT SOLEUS MUSCLE FIBERS AS DEMONSTRATED BY HISTOCHEMICAL STAINING AND ELECTROPHORESIS

Abstract

A histochemical stain for heart type lactic dehydrogenase (LDH) has been correlated with the electrophoretic isoenzyme pattern. The rat soleus was chosen for this study since a minority of its fibers contain LDH which is inhibited by urea in the histochemical system. This minority group has attracted attention because they stain intensely for both phosphorylase and succinic dehydrogenase. Electrophoresis of LDH from fibers dissected from freeze-dried sections revealed that the bulk of the soleus fibers contain primarily isoenzymes I and II with a trace amount of III and practically none of IV and V. The isoenzyme pattern obtained from the minority group of fibers stained most intensely for isoenzyme III. Isoenzyme II gave a moderate reaction while isoenzymes I and IV reacted weakly and isoenzyme V was not detectable. Taken with other observations these results indicate that in the histochemical system containing 4 molal urea a strong reaction in rat tissues is evidence of a preponderance of isoenzymes I and perhaps II.