Haematological studies on 90Sr-90Y-toxicity: II. Femoral CFU-s kinetics and mitogen response of spleen cells.

Ferrokinetic perturbations in peripheral blood of mice treated with 90Sr-90Y were demonstrated previously. This paper deals with the effects of 90Sr-90Y treatment (2.5, 5, and 10 microCi/mouse), on the haemopoietic stem cell compartment and on the immune-status. The frequency and kinetics of haemopoietic stem cells in femoral marrow (determined as colony forming units in spleen, CFU-s) and their haemopoietic efficiency (as gauged by 59Fe- and 125IUdR-uptake) were estimated. The responsiveness of splenic lymphocytes of the same animals to mitogens (Con A, PHA, and LPS) were also measured. In all assays striking dose-dependent changes marked either by depressions or overshoots were observed during the first week post-incorporation. These are correlated with the pattern of deposition (primary and secondary) of the radionuclides 90Sr-90Y. Towards the end of the period of observation and presumably thereafter, the dependence on dose disappeared and the values remained subnormal. An exception to this was the response of splenic lymphocytes to mitogens. Much higher reactivity was recorded up to the end. This higher reactivity is attributed to augmented cellular turnover, the newly recruited lymphocytes (in accord with thier extreme radiosensitivity), being probably more reactive.