Right brain regions of anesthetized rats were loaded with [3,5,7-3H]methotrexate ([3H]MTX) or with [14C]sucrose by infusing the tracers into the right carotid artery, after the blood-brain barrier had been opened by right carotid infusion of a hypertonic arabinose solution. During the 6 hr following the procedure, the [3H]MTX concentration in 7 right-sided brain regions, when normalized to the plasma concentration integral during tracer infusion, fell, with an average half-time of 4.8 hr as compared to less than 20 min for the initial rate of loss of [14C]sucrose. Right-left brain concentration differences 3 hr after treatment were statistically significant (p < 0.05) for [3H]MTX but not for [14C]sucrose. The results indicate that intracerebral [3H]MTX is lost more slowly than is intracerebral [14C]sucrose, possibly because [3H]MTX enters brain cells, whereas [14C]sucrose remains largely extracellular.
↵1 Supported in part by NIH Grant CA 27191 and the Veterans Administration.
↵2 To whom requests for reprints should be addressed.
- Received January 19, 1981.
- Accepted November 6, 1984.
- ©1985 American Association for Cancer Research.