Carnitine and short-chain acylcarnitines in the lumen of the human male reproductive tract.

Bioautography of human semen demonstrated the presence of L-carnitine, acetylcarnitine, propionylcarnitine and C4-acylcarnitines (butyrylcarnitines). In studies designed to ascertain the organs secreting these compounds into semen it was found that: Quantitative analyses of semen obtained pre- and post-vasectomy showed markedly decreased L-carnitine concentrations, slightly decreased acetylcarnitine levels, and unchanged propionyl- and butyrylcarnitine concentrations as a result of vasectomy. The earlier portion of human split ejaculate samples characteristically contained higher concentrations of carnitine and its propionyl- and butyryl esters and a lower concentration of acetylcarnitine than did the later portion. Vas deferens luminal fluid contained carnitine and each of the short-chain acyl derivatives, as shown by bioautography. Prostatic fluid contained only small amounts of carnitine and its derivatives. Spermatozoa contained much more acetylcarnitine than free carnitine, and only trace amounts of the other acylcarnitines. It is concluded that carnitine in semen is secreted primarily by the epididymis, that a proportion of the acetylcarnitine derives from the seminal vesicles and epididymis, and that propionylcarnitine and butytylcarnitine enter semen, at least in part, together with the vas deferens contents.