A Cytochemical Study of Lipid, Glycogen and Lactate Dehydrogenase in the Developing Liver.

In recent studies the lactate dehydrogenase (LDH) isozymes of adult (Lindsay, '63) and embryonic (Philip and Vesell, '62; Nebel and Conklin, '64) chick liver were demonstrated. A maximum of six isozymes were found in the embryonic liver while four isozymes were present in the liver after hatching. While several theories (Apella and Markert, '61; Markert, '62; Cahn et al., '62; Fritz and Jacobson, '63) have been proposed to account for the number of isozymes, there have been few studies which have attempted to correlate LDH isozymes with either intracellular distribution (Allen, '61) or metabolic function (Lindsay, '63; Plagemann et al., '60). The fact that the major changes in the LDH isozymes were noted during the period from the sixth to the twelfth day of development, the time of onset of carbohydrate and lipid metabolism in hepatic cells of the chick (Dalton, '37), suggested a possible correlation between these events. Furthermore, the isozyme changes might be associated not only with the onset of specific function but also with changes in the intracellular distribution of lactate dehydrogenase. In the present study the intracellular deposition of glycogen and lipid and the localization of lactate dehydrogenase activity were demonstrated in order to determine whether any of these factors could be correlated with the isozyme pattern previously reported (Nebel and Conklin, '64). In addition, the application of histochemical methods for revealing LDH activity afforded the opportunity to evaluate certain current problems of histochemical technique, i.e., the use of formalinfixed (Walker and Seligman, '63) vs. acetone extracted (Hitzeman, '63) vs. fresh tissue for the demonstration of oxidative enzyme activity. Finally, in spite of increasing evidence to the contrary (Schnei-