Physiological characteristics of serotonin transporters on rat platelets.

Physiological characteristics of serotonin (5-hydroxytryptamine, 5HT) transport through the platelet membrane was investigated in Wistar rats with our recently developed method permitting repetitive measurements of transporter kinetics in individual animals. Full kinetic analysis in the population of 91 animals revealed Michaelis constant (K(m)) of 0.158 +/- 0.025 microM and maximal velocity (Vmax) of 5HT uptake of 225 +/- 32 pmol per 10(8) platelets min-1 (mean +/- S.D.). Both kinetic parameters demonstrated normal distribution curves, which for Vmax were slightly skewed toward higher than average values. No gender effect was shown in frequency distributions, mean values and variability of kinetic parameters. A significant intraindividual correlation between kinetic parameters was found suggesting compensation at the level of the plasma membrane. Kinetic parameters were not influenced by age (until the middle age) or annual cycle (under laboratory conditions) and were shown to be fairly stable in time, supporting the view that platelet 5HT transport kinetics could be a useful biological trait marker.