SURVIVAL OF SKIN TRANSPLANTS IN RATS TREATED WITH AZATHIOPRINE

Survival time of skin homografts under treatment with azathioprine has been examined in 268 rats. The results are as follows: 1. At a dosage up to 48 mg/kg/day during a 20 days' treatment azathioprine has a lethality of about 20 per cent. It is increased by higher daily doses. 2. Pretreatment with azathioprine has a disticnt favourable influence on mean survical time of skin homotransplants. 3. In order to obtain immunosuppression a certain threshold concentration of azathioprine is necessary so that a daily minimum dose (of about 40 mg/kg/day) has to be applicated. 4. There exists no exact linear relationship between toxicity and immunosuppression in azathioprine. 5. When azathioprine is administered at a maximum dosage, mean survival time of homografts is prolonged from 7,2 days in control animals to 15.1 days. Lethality amounts to 42 per cent.. © 1969 Springer-Verlag.