Uptake of tritiated methotrexate by mouse brain tumors after intravenous or intrathecal administration

✓ Malignant gliomas were induced in strain ddN mice by intracerebral implantation of a 20-methylcholanthrene pellet. The uptake and distribution of tritiated methotrexate (MTX- 3 H) in the tumor were investigated by radioactive assay and radioautography after single intravenous or intrathecal injections. By either route, a large amount of MTX- 3 H was taken up by gliomas, and a significantly higher concentration was observed in tumor than in the brain tissue. At 24 hours after intrathecal administration, the uptake of MTX- 3 H by gliomas exceeded that achieved after intravenous injection, although the drug dosage in the latter was 10 times that in the former.