Effect of Splenic X‐Irradiation on Bone Marrow Function: Experimental Studies of a Serum Mitotic Inhibitor in Rabbit and in Patients with Chronic Myelocytic Leukaemia

Abstract

S ummary . The effect of a selective splenic irradiation on bone marrow function was studied in rabbits given a single splenic exposure with 300 r. of X‐rays. Serum collected shortly thereafter decreased mitotic activity in suspensions of normal rabbit bone marrow. This in vitro inhibitory effect was only transiently demonstrable in the serum appearing 2 hours after irradiation and disappearing 3 hours later. Five patients with chronic myelocytic leukaemia in relapse receiving splenic radiotherapy in large single doses of 200–400 r. (surface dose) were studied along these lines. Serum collected 3 hours after X‐ray treatment was tested with suspensions of normal bone marrow and was found to decrease erythroblastic mitotic activity significantly below the control values observed with serum collected before irradiation. The magnitude of this in vitro effect was to some extent related to the spleen size and the radiation dose. No differences were observed between bone marrow suspensions incubated with pre‐irradiation leukaemic serum and normal control serum.