Uptake of piperidine and pipecolic acid by synaptosomes from mouse brain

摘要

Piperidine is actively transported into the synaptosomal fraction of adult mouse brain. The transport mechanism appears to be Na+independent but is temperature dependent and sensitive to ouabain. Analysis of kinetic experiments indicates only a “low-affinity” transport system to be present. By contrast the uptake ofD,L-3Hpipecolic acid at a concentration of 4×10−7M was temperature and Na+dependent, ouabain sensitive, and revealed a two-component system with aKm=3.9±0.17×10−6M,Vmax=129±6 pmol/mg protein/3 min for the “high-affinity” system and aKm=90.2±4.3×10−6M,Vmax=2.45±0.19 nmol/mg protein/3 min for the “low-affinity” system. Compounds structurally related to pipecolic acid such as glycine,l-proline, 4-amino-n-butyric acid, and 5-amino-n-valeric acid showed an inhibitory effect on uptake at a concentration of 10−4M. The demonstration of biosynthesis of pipecolic acid in mouse brain and the presence of a “high-affinity” sodium-dependent uptake system suggest a physiological role of this substance