Increase in the Penetration of Tracer Compounds into the Rat Brain during 2‐Methyl‐4‐Chlorophenoxyacetic Acid (MCPA) Intoxication

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Abstract
The penetration of different i.v. tracer molecules such as 14C-2-methyl-4-chlorophenoxyacetic acid (14C-MCPA), 14C-p-aminobenzoic acid (14C-PABA), 14C-sucrose, 14C-antipyrine and iodinated (125I) human albumin (125I-HA) into the brain and CSF was studied in MCPA-intoxicated and control rats. Toxic s.c. doses of Na salt of MCPA (200-500 mg/kg) increased highly the brain/plasma and CSF/plasma ratios of 14C-MCPA and 14C-PABA, as compared to the muscle/plasma ratio. Probenecid (200 mg/kg) did not affect the cerebral MCPA concentration in the intoxicated animals. The tissue/plasma ratios of 14C-sucrose, 14C-antipyrine and 125I-HA were also increased in the brain and CSF of intoxicated animals but the increases were less pronounced than those of 14C-MCPA or 14C-PABA. MCPA intoxication caused a selective damage of the blood-brain barrier.