Kinetic parameters for transport of L-carnitine in rat aortic endothelial cells.

Total (TTC) and saturable (TSC) transport of L-carnitine and the Na+-dependent (Na+dep) and Na+-independent (Na+indep) components of transport (0–80 µmol/L L-carnitine, 3 µCi/mL L-[3H]carnitine, 30 seconds, 37°C, pH 7.4) were measured in cultured (passage 2) rat aortic endothelial cells (RAECs) from normotensive (WKY) or spontaneously hypertensive (SHR) rats as described in Methods. The initial velocity (vi) was measured for 20 µmol/L L-carnitine up to 30 seconds. vi, initial velocity (pmol/µg protein/second); Vmax, maximal velocity (pmol/µg protein/minute); Km, apparent Michaelis-Menten constant (µmol/L); Vmax/Km, maximal transport capacity (pmol/µg protein/minute/(µmol/L)); KD, lineal, non-saturable transport in the range of L-carnitine concentrations used in this study (pmol/µg protein/minute/(µmol/L)). *P<0.05 versus corresponding values in WKY, †P<0.05 versus corresponding values for Na+dep in SHR or WKY rats. Values are mean ± SEM (n = 15).