Cell Proliferation Kinetics of Endogenous and Exogenous Erythroid Spleen Colonies in Lethally Irradiated Mice

Abstract

Summary. Two tvpes of .spleen eoloii}' fi)niiation ha\e been f()iiipart.'d with respect to the kinetiLs nf er\thn>id cells. KndoHenoiis colonies were obtained using phenjihydrazhie treatment followed by lethal total body irradiation und exogenous colonies derived from normal bone marrow transplanted into irradiated animals. Individual colonies of both endogenous and exogenous types were scored for ''HTdR labelling index (LI), mitolic index (MI) and \ineristine niitotic accunuilatioii. There was no significant dilierence in kinetic beha\'iour of erythroid colonies in the endogenons compared with the e.\ogenoiis situation.Erythroid colonies from both endogenous and exogenous sonrees were classified into three separate groups, "early", "intermediate" and "late" on the basis of their inori) ho logical appearanee. When this classification was later taken into account there were no differences in kinetic behaviour between "early", "intermediate" and "late" colonies of endogenous as comparctl to the respective classes of exogenous colonies. Labelling indices of "early", "intermediate" and "late" colonies fell into three distinct groups ha\ing mean corrected labelling indices of approximately 15%. b3% and 47'/, rcspecti\el\. The mean nuclear diameter of cells in "early" colonies was significantK-greater than of cells in "intermediate" and "late" colonies, cells of the latter two having similar mean nuclear diameters.The only significant difference observed between the endogenous and exogenous colonies was that the erythroid to granulocytic colony ratio was considerably higher for endogenous colonies. This ma\-be attributed to the presence of an environment more fa\ourable to er>throid ile\elopinent in spleens of miee which ha\e haemoKtic anaemia.INTRODUCTION.