Comparative studies of the isozymes of lactic dehydrogenase in rabbit and man. Observations during development and in tissue culture

Changes in the lactate dehydrogenase isoenzyme pattern during differentiation of rabbit bone-marrow erythroid cells

1. Differentiation and maturation of rabbit bone-marrow erythroid cells was accompanied by a 15-fold decrease in lactate dehydrogenase activity from approx. 0.1pmol of NADH utilized/min per cell in basophilic cells to 0.007 pmol of NADH/min per cell in reticulocytes. 2. In early cells, cell division takes place with a corresponding decrease in cell volume, but the concentration of lactate dehydrogenase remains almost constant. 3. When cell division ceases, qualitative as well as quantitative changes in the lactate dehydrogenase isoenzyme pattern become apparent and reticulocytes were found to contain almost exclusively the H4 isoenzyme, whereas early erythroblasts contained also the M4 and hybrid isoenzymes. 4. Extracts from a lysosome-enriched subcellular fraction of bone-marrow erythroid cells specifically degraded the M4 isoenzyme in vitro, but the H4 form was stable. It is suggested that lysosomal enzymes are involved in bringing about the observed changes in lactate dehydrogenase isoenzyme patterns in vivo.

Gene dosage effect in human triploid fibroblasts

The activity of 13 cytoplasmic enzymes has been determined in fibroblast extracts from 9 triploid and 13 control lines. The results show a high activity for 2 X-linked enzymes, glucose 6-phosphate dehydrogenase and phosphoglycerate kinase. These data, together with cytogenetic observations, support the contention that 2 X chromosomes were active in the triploid lines.

Identification of cells in culture

Most laboratories using cells cultured in vitro maintain multiple cell lines. Such lines should be monitored for species and intraspecies characteristics to prevent invalidation of research work due to incidents of cell line cross-contamination. This report describes the results obtained when 246 cell cultures were examined for evidence of cross-contamination or mislabeling. Using species-specific antigens, isoenzyme electrophoresis, and chromosomes as markers of identity, 14% of the cultures submitted were found to be contaminated by cells of another species. Of human cell lines submitted 25% were of HeLa cell origin, as determined by 2 intraspecies markers, glucose-6-phosphate dehydrogenase and chromosome analyses. The fact that, overall, nearly 30% of the cell lines examined were incorrectly designated makes the importance of cell line monitoring self-evident.

Constitution, viability, and lactate dehydrogenase in stationary-phase L-cell suspension cultures

Starved suspension cultures of L cells exhibit a plateau phase of short duration followed by loss of key cellular constituents and rapidly decreasing viability. In contrast, regularly fed,. undiluted cultures remain stationary at a high cell density for prolonged periods without structural alterations or loss of viability. The L cells contain a single lactate dehydrogenase isozyme with an electrophoretic mobility similar to that of lactate-dehydrogenase-5. High-density stationary cultures show a tenfold increase of the specific activity of this enzyme and a recurrent biphasic pattern of carbohydrate utilization with, first, production and, later, consumption of lactate.

Formation of human lactate dehydrogenase isozyme patterns in vitro

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