Comparison of in vitro and in vivo cell cycle parameters of lymphoid cells in pig spleens.

Parameters of the cell cycle of lymphoid cells were estimated by analyzing percent labeled mitoses curves after a 3H-thymidine flash. Either anaesthetized pigs were labeled and multiple biopsies taken from the spleen in vivo or isolated perfused pig spleens were labeled in vitro. The data from in vivo and in vitro experiments were very similar. The mean values for cell cycle parameters were: 20.2 to 20.5 hours for the generation time, about 0.5 to 1 hour for G2, about 1.2 to 1.3 hours for M; about 17 to 16.4 hours for S and about 1.5 to 1.7 hours for G1. The mean grain count halving time of labeled mitoses was in accordance with the measured generation time. The isolated perfused spleen seems to give results equal to in vivo data and could, therefore, be employed as a model for studying cell cycle parameters not only in animal but also in human lymphoid tissue.