PLACENTAL TRANSFER AND FETAL DISTRIBUTION OF MESCALINE-¹⁴C IN MONKEYS

¹ Texas Research Institute of Mental Sciences, Houston, Texas

Third trimester pregnant Saimiri sciureus monkeys were injected i.v. with 5 mg/kg of mescaline-¹⁴C-HCl and sacrificed after 10 minutes or , 1, 2, 3, 6 or 16 hours. The placental transfer and fetal distribution of radioactivity were studied using autoradiography and liquid scintillation spectrometry. The percentage of unchanged compound and of specific metabolites was determined in the maternal liver using thin-layer chromatography. Mescaline crosses the placental barrier in the monkey. The passage of mescaline across this barrier is limited, however, by the high ionization (99.3%) of mescaline at physiological pH and by the low lipid solubility of the un-ionized form of mescaline. Among the fetal tissues, relatively high concentrations of radioactivity were found at 10 minutes in the liver, lung and thyroid, at one-half and one hour in the gastrointestinal tract and liver and at the later times in the gastrointestinal tract, eye and kidney. The fetal blood, brain and cerebrospinal fluid always contained relatively low concentrations of radioactivity. Through the first six hours, less than 25% of the radioactivity found in the maternal liver consisted of mescalime metabolites. N-acetylmescaline was the major metabolite identified. Other metabolites identified were 3,4,5-trimethoxyphenylacetic acid and 3, 4, 5-trimethoxyphenylethanol.