[Chromosome examination in children of parents treated with Imuran]

Azathioprine, a clastogen in human somatic cells? Analysis of chromosome damage and SCE in lymphocytes after exposure in vivo and in vitro

Chromosomal analyses in lymphocytes of 28 patients with multiple sclerosis were carried out before, during and after Azathioprine (Aza) therapy. Only a higher incidence of gaps was found in treated patients than in a group of healthy persons but not in comparison with untreated patients. Similarly, no significant clastogenic effect was observed in vitro after short-term and long-term treatment of unstimulated and stimulated lymphocytes with concentrations of 1--100 microgram Aza per ml. Treatment of cultures with 0.0001--4.0 microgram/ml did not yield increased SCE frequencies. The absence of any significant clastogenic effect of therapeutic doses of Aza on human somatic cells is deduced from an evaluation of previously published data and from the present results.

Investigation into the mutagenic activity of azathioprine (Imuran) in different test systems

The chromosome-damaging effect of azathioprine (Imuran) was investigated in the micronucleus test with mice and rats, in the pertussis-stimulated lymphocyte metaphase test with rabbits, and in children on azathioprine therapy. In the micronucleus test, there was a dose-dependent increase in the number of cells with micronuclei. The dose was given twice in 24 h, i.p., 25, 50 and 100 mg/kg body weight for mice, and 50, 100 and 200 mg/kg for rats. In the lymphocyte test, a dose of 5 and 20 mg azathioprine per kg body weight was given orally to rabbits on three successive days after pertussis injection. Compared with treatment in the control group these treatments induced a significantly increased number of cells with chromosomal abnormalities. These results were confirmed in lymphocyte cultures of children on long-term azathioprine therapy after kidney transplantation, where an increase in the number of structural chromosomal abnormalities was observed.