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In the male reproductive tract, very high concentrations (mmol l−1) of free l-carnitine and acetyl-l-carnitine are found in the epididymides, seminal plasma and spermatozoa. It has been reported that the uptake of free l-carnitine by spermatozoa might be related to the epididymal maturation of the sperm membrane, since a greater uptake was found by caput than by cauda spermatozoa in vitro. However, the free l-carnitine concentrations estimated inside the gametes were never greater than those of the surrounding medium. In this study, we investigated the mechanism of transport of free l-carnitine and its ester acetyl-l-carnitine, through the plasma membrane of mature and immature epididymal boar spermatozoa. In vitro, we found a passive diffusion of both compounds to the spermatozoa, whatever the maturation stage. The spermatozoa might progress in the epididymal lumen and accumulate high amounts of free l-carnitine. The active uptake of free l-carnitine occurs only across epididymal mucosa. These results are in agreement with those reported on cells of other organs that exchange pharmacological free l-carnitine concentrations (mmol l−1) by a passive mechanism through the plasma membrane. The acetylation of high amounts of free l-carnitine inside the spermatozoa was found only in caudal spermatozoa. This result suggests that oxidative metabolism (producing acetyl CoA) might be more active in mature cells. The acetyl-l-carnitine added to the incubation medium of boar spermatozoa was hydrolysed. Enzymatic activity of the sperm membrane is low and this may partially explain the low concentrations of acetyl-l-carnitine found in the caudal epididymal plasma.
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Summary. The prostaglandins, PGE-1, PGE-2, PGF-1α, PGF-2α, 19-OH-PGE-(1 + 2), 19-OH-PGF-α were estimated by RIA in the semen of (a) normal men of proven fertility (total semen or split ejaculate); (b) men 1 year after vasectomy; and (c) men with agenesia of the vas deferens and seminal vesicles. PG concentrations in the semen of vasectomized men were largely within the normal ranges. In men with agenesia of the vas deferens and seminal vesicles, PG concentrations were 102–105-fold less than that measured in normal subjects. The patterns of 19-OH-PGs and PGF-α in the five fractions of a split ejaculate followed in general the fructose profile. These data suggest that prostaglandins mostly originate in the seminal vesicles.
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Summary. In the epididymal fluid of boars, the concentration of carnitine (nmol/mg protein) began to increase from 20 in the distal caput, then rose progressively to 700 in the distal cauda. By contrast, the carnitine content of spermatozoa only started to increase in the proximal cauda where the concentration of carnitine in the fluid was 200–300 nmol/mg protein then gradually increased in spermatozoa from more distal sites. The increase in the acetylcarnitine content of spermatozoa paralleled that of the carnitine amount and represented 50% of the total carnitine (carnitine + acetylcarnitine). We conclude that the acetylcarnitine content of epididymal spermatozoa may be used as a marker of maturation.
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Summary. Gossypol acetic acid (20, 25 or 30 mg/kg/day orally for 5 weeks) decreased epididymal weight in adult Sprague–Dawley rats but the epididymal concentrations of proteins, lactate dehydrogenase and acid phosphatase were unchanged. The concentrations of carnitine, inositol and potassium in epididymal fluid were decreased in a dose-related manner. These modifications were not due to disturbances of Leydig and Sertoli cell functions which were normal. We suggest that the reduction in epididymal secretion results from a decrease in the number of spermatozoa rather than from a direct action of gossypol on the epididymal epithelium.
Keywords: gossypol; rat; epididymis; carnitine; inositol
