[The effect of barbiturates and diphenylhydantoin on the mitotic activity of thymocytes and bone marrow cells in mice and rats].

Phenobarbitone (PB) and diphenylhydantoin (DPH) inhibited the mitotic rate of thymocytes and bone marrow cells (colchicine blocked metaphases) dose- and time-dependent (20-80 mg/kg i.p., 12-48 hours) in mice and rats in vivo. The inhibition of proliferation was evident also after repeated administration of the drugs and other barbiturates. Other substances with a depressive effect on the central nervous system (etomidate, ketamine, chlorpromazine and ethanol) did not influence the mitotic rate of the thymocytes. Inhibition of the mitotic rate by PB was also observed in adrenalectomised rats. In vitro PB and DPH inhibited the mitotic rate of thymocytes in therapeutic and toxicologically relevant concentrations (10(-5)-10(-3) mol/l). The investigations indicate a direct effect of PB and DPH on rats. Possible immunosuppressive effects are discussed.