title: [3H]Methotrexate loss from the rat brain following enhanced uptake by osmotic opening of the blood-brain barrier.
abstract: 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 [14C]sucrose. Right-left brain concentration differences 3 hr after treatment were statistically significant (p less than 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.
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D002250:Carbon Radioisotopes; D008297:Male; D008433:Mathematics; D008727:Methotrexate / Q000378:metabolism*; D009995:Osmosis; D051381:Rats; D013395:Sucrose / Q000378:metabolism; D014316:Tritium
chemical_list: D002250:Carbon Radioisotopes; D014316:Tritium; D013395:Sucrose; D008727:Methotrexate