On the variation in lactate dehydrogenase activity of Burkitt's lymphoma cells in suspension culture.

• 1.1. Sampling of cell populations from non-synchronous and synchronous cultures of Burkitt's lymphoma cells revealed a marked degree of variation in lactate dehydrogenase (LDH) activity during all growth stages.
• 2.2. Rapid changes in the LDH isoenzyme composition in both non-synchronous and synchronous cultures were also detected in these experiments.
• 3.3. The variations in LDH activity were not invariably accompanied by altered levels of soluble protein, and tests for the presence of activators and inhibitors of LDH activity in these cultures were undertaken.
• 4.4. Thermolabile factors which were capable of elevating or depressing the activity of solutions of purified LDH were identified and partly characterized.