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

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Abstract
The development of enzyme activity and isozyme distribution of lactate dehydrogenase (LDH) was studied in murine organotypic hippocampal slice cultures and dissociated cultures of neocortical neurons and cerebellar granule cells and compared with that of the respective brain regions invivo. In the hippocampal slice cultures and the hippocampus invivo, the activity of aspartate aminotransferase (AAT) was also measured. During development in culture the specific activity of LDH increased in all types of cultures reaching values similar to that found in the corresponding brain areas invivo. However, significant differences in the isozyme distribution were observed between the preparations in vitro and invivo. During development invivo, the LDH isozyme pattern 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 activity. The cultured cerebellar granule cells did not express the H4-isozyme at all, while in the hippocampal slice cultures and the cultured neo-cortical neurons this isozyme accounted for about 5% of the total LDH activity. The activity of AAT in the hippocampal organotypic slice cultures increased considerably during the culture period in parallel with the increase in AAT activity during postnatal development of hippocampus invivo. The activity of AAT in the slice cultures was, however, consistently lower than the corresponding activity invivo. The results show that perinatal hippocampal tissue and neurons from neocortex or cerebellum retain their immature LDH-isoenzyme distribution when grown as organotypic slice cultures or dissociated cell cultures, respectively. This lack of shift from the M4 to the H4 LDH isozyme which is typical of tissues relying on aerobic glycolysis has several implications but does not apparently interfere with the otherwise normal differentiation of morphological, biochemical and electrophysiological characteristics of these preparations.