[Lactate dehydrogenase isoenzymes in the growth of heart cells]

As part of a detailed biochemical study of developing and growing heart cells, the protein- or cell-specific activities of lactate dehydrogenase isozymes were determined in cultured neonatal hamster heart cells and in intact hearts of hamster embryos and neonates. Evidence for differentiative growth of heart cells in both systems was obtained, but the characteristic in vivo isozyme shift from species rich in M subunits to those containing mainly H subunits was reversed in the cultured cells, suggesting that controls normally determining this pattern change might be absent in the conditions of in vitro cultivation.