title: Evidence of stereospecificity in the in vivo methylation of [14C](+/-)-nicotine in the guinea pig.
abstract: In vivo metabolism of [14C]nicotine to N-methylnicotinium ion in the guinea pig appears to be a stereospecific biotransformation, involving only the R-(+)-isomer. The detection and quantitation of urinary radiolabeled nicotine metabolites after ip injection of either [N-14CH3](+/-)-nicotine or [2'-14C](+/-)-nicotine, was carried out on an HPLC cation-exchange analytical system. Utilizing the recently discovered phenomenon of differential enantiomeric association, the stereo-chemistry of the methylation pathway was determined. Significant differences in the tissue distribution of 14C label from the [N-14CH3]-vs. [2'-14C]nicotine-treated animals were observed 24 hr after nicotine administration. An unidentified metabolite with high affinity on cation-exchange chromatography, was detected as a metabolite of [2'-14C](+/-)-nicotine, but was not observed as a metabolite of [N-14CH3](+/-)-nicotine.
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D006168:Guinea Pigs; D008297:Male; D008745:Methylation; D009538:Nicotine / Q000378:metabolism* / Q000652:urine; D013237:Stereoisomerism; D014018:Tissue Distribution
chemical_list: D009538:Nicotine