Uptake of 3H-L-carnitine by isolated rat epididymal tubules.

The uptake of radiolabeled L-carnitine has been studied in isolated epididymal tubules from the rat. The uptake of 3H-L-carnitine increases with a temperature coefficient KT of 0.22 nmol carnitine.mg protein-1 in the intermal 22--31 degrees and with a low uptake at 4 degrees C. The uptake of radiolabeled carnitine (as percent) is reduced at high concentrations of L-carnitine, by deoxycarnitine but not by D-carnitine. This uptake mechanism is especially active in the distal caput and corpus segments of the epididymis. Thus, an uptake mechanism for carnitine is present in the epididymal cells which besides the carnitine uptake in spermatozoa is responsible for the dramatic increase in carnitine concentration in cauda epididymis.