title: Absorption by the rhesus monkey of phenylalanine methyl ester and species differences in its metabolism by blood, plasma and intestinal mucosa.
abstract: Phenylalanine methyl ester (PM) is a decomposition product of the sweetening agent aspartame. The potential for absorption of PM was examined following intragastric and intraduodenal administration of 20-mg doses of [14C]PM to rhesus monkeys implanted with hepatic portal vein cannulae. Small amounts of unchanged PM (less than 0.1 micrograms/ml) were detected in portal and peripheral blood samples during the first 1-2 hours after administration, but none was detectable (less than 0.001 micrograms/ml) at later times. Comparison of the areas under the PM and total 14C blood concentration-time curves indicated that only 0.2% of the administered PM reached the portal blood unchanged, and 0.1% or less reached the peripheral blood unchanged. Blood and plasma from monkeys and humans hydrolyzed PM in vitro at very similar rates, but plasma PMase activity was much higher in the dog and rat than in the monkey or human. Hydrolysis of PM by intestinal mucosa homogenates was also faster for the rat and dog than for the monkey. The in vitro results suggest that absorption of intact PM in the human would be no greater than that found in the monkey.
mesh_terms: D000818:Animals; D004285:Dogs; D005260:Female; D006801:Humans; D006868:Hydrolysis; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism*; D008253:Macaca mulatta; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism; D051381:Rats; D013045:Species Specificity
chemical_list: C034515:phenylalanine methyl ester; D010649:Phenylalanine