EFFECT OF LACTIC-ACID ON THE KINETICS OF GROWTH AND ANTIBODY-PRODUCTION IN A MURINE HYBRIDOMA - SECRETION PATTERNS DURING THE CELL-CYCLE

The effects of elevated lactic acid concentration on the cell cycle ki netics of hybridoma cell growth and antibody production in batch cultu re were studied using conventional methods based on population-average data analysis and using now cytometry based on single-cell data analy sis. When 33 mM lactic acid was initially present, the true specific g rowth rate was reduced by 37% and the cell specific antibody productio n rate increased by a factor of 2.6 relative to a control culture with no additional lactic acid. DNA content distributions measured during balanced exponential growth were not affected by lactic acid concentra tion indicating lactic acid has a uniform effect on cell growth throug hout the cell cycle. There was little or no effect on single-cell dist ributions of intracellular antibody content measured for the total pop ulation and for each cell cycle phase. The net rate of total antibody synthesis was found to be independent of specific growth rate. This im plies that the balance of the total amount of antibody synthesized is shifted from cellular accumulation towards secretion when specific gro wth rate decreases. Our data predict that a maximum specific secretion rate of 2.7 pg per cell per h could be achieved if the specific growt h rate was reduced to zero. The rates of secretion in the G(1) and S p hases increased with decreasing specific growth rate, while the rate o f secretion in the G(2) + M phase remained relatively constant. Under the assumptions that (a) at the fastest growth rate, secretion in the G(1) phase is negligible and (b) the rate of synthesis increases expon entially as cells proceed from the S phase to the G(2) + M phase, our data predict that for the slowest growth rate, the rate of secretion i n G(2) + M is approx. 3-times that in the G(1) phase and 5-times that in the S phase.