A DEVELOPMENTAL-STUDY OF LACTATE-DEHYDROGENASE ISOZYME AND ASPARTATE-AMINOTRANSFERASE ACTIVITY IN ORGANOTYPIC RAT HIPPOCAMPAL SLICE CULTURES AND PRIMARY CULTURES OF MOUSE NEOCORTICAL AND CEREBELLAR NEURONS

The development of enzyme activity and isozyme distribution of lactate dehydrogenase (LDH) was studied in murine organotypic hippocampal sli ce cultures and dissociated cultures of neocortical neurons and cerebe llar granule cells and compared with that of the respective brain regi ons in vivo. In the hippocampal slice cultures and the hippocampus in vivo, the activity of aspartate aminotransferase (AAT) was also measur ed. During development in culture the specific activity of LDH increas ed in all types of cultures reaching values similar to that found in t he corresponding brain areas in vivo. However, significant differences in the isozyme distribution were observed between the preparations in vitro and in vivo. During development in vivo, the LDH isozyme patter n changed from a preferential M-subunit composition to a preferential H-subunit composition regardless of the brain area. This shift was not observed in the respective cultures where the M4-isozyme prevailed at all culture periods examined accounting for 30-45% of the total LDH a ctivity. The cultured cerebellar granule cells did not express the H4- isozyme at all, while in the hippocampal slice cultures and the cultur ed neo-cortical neurons this isozyme accounted for about 5% of the tot al LDH activity. The activity of AAT in the hippocampal organotypic sl ice cultures increased considerably during the culture period in paral lel with the increase in AAT activity during postnatal development of hippocampus in vivo. The activity of AAT in the slice cultures was, ho wever, consistently lower than the corresponding activity in vivo. The results show that perinatal hippocampal tissue and neurons from neoco rtex or cerebellum retain their immature LDH-isoenzyme distribution wh en grown as organotypic slice cultures or dissociated cell cultures, r espectively. This lack of shift from the M4 to the H4 LDH isozyme whic h is typical of tissues relying on aerobic glycolysis has several impl ications but does not apparently interfere with the otherwise normal d ifferentiation of morphological, biochemical and electrophysiological characteristics of these preparations.