Detailed kinetic analysis of Shay chloroleukaemia cell population propagated in permanent suspension culture in vitro.
Detailed kinetic analysis of a growing cell population is difficult, even when assay conditions are nearly ideal. Therefore, it is usually essential to perform several types of experiments and analyse all the results in terms of a mathematical model, the use of which is not limited a priori by a specified application. In the present study we investigated cell population kinetics using rat chloroleukaemia cells propagated in suspension culture in vitro. The parameters were measured: doubling time of the population, fraction of labelled mitoses, changes in labelling index with time after pulse labelling, continuous labelling and stathmokinetic index. Analysis of the results was based on a computer program CECAM, which is a stochastic model capable of simulating essentially all types of kinetic experiments based on presently known assay techniques. The results showed that precise and reliable information on cell population kinetics could not be obtained from the analysis of any single type of experimental data. In particular, the technique of labelled mitoses underestimated the duration of the G1 phase, owing to subtle label-induced changes in population behaviour. These changes could not have been detected with any certainty without rigorous quantitative comparisons with other types of experimental data. As a whole, however, results obtained by the different techniques were in agreement and the kinetic behaviour of chloroleukaemia cells in vitro could be established in detail. In certain circumstances even minute changes in the kinetic parameters of the cells can modify population behaviour drastically. To study these cases adequately the experiments must be designed with utmost care, preferably with the aid of preceding simulations. This is because demonstration of small primary changes in population kinetics may be beyond the limit of detection of any single assay method.