Free L-carnitine in human seminal plasma

It has often been suggested that determination of free L(—)-carnitine in seminal plasma may provide a good indication of epididymal function. However, there has been disagreement regarding the origin of L(—)-carnitine (epididymis and seminal vesicles) and its concentration in human seminal plasma. In this study, free L(—)-carnitine was determined after deproteinization with an enzymatic spectrophotometric method. In 29 semen samples from fathers and with normal spermiograms (semen volume between 2 and 6 ml, sperm count over 20.10⁶/ml, more than 50% motile spermatozoa), the total free L(—)-carnitine in the seminal plasma was 1010 nmoles (SD:±480), in 16 samples from vasectomized men it was 131 nmoles (SD:±77), and in 5 from men with agenesis of the vas deferens and seminal vesicles it was 21 nmoles (SD:±25). These results suggest that free L(—)-carnitine in the seminal fluid is predominantly of epididymal origin. The results of free L(—)-carnitine determinations in split ejaculates and the absence of a correlation between L(—)-carnitine and fructose concentrations in semen from normal subjects indicate that the seminal vesicles make only on minor contribution to L(—)-carnitine in the seminal plasma.