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Search for other papers by J. A. Blaquier in
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Summary. Zona-free hamster oocytes were used to evaluate the penetrating capacity of spermatozoa recovered from the caput, corpus and cauda segments of 5 human epididymides. The ability of spermatozoa to bind tightly to oocytes increased in spermatozoa from successive segments. However, only spermatozoa recovered from the cauda epididymidis were able to penetrate the oocytes (26%). These results suggest that, in man, a gradual process of sperm maturation occurs in the epididymis, as has been observed in numerous other species of mammals.
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Summary. The ability of spermatozoa recovered from the successive segments of the hamster epididymis to bind to the zona pellucida was studied and a major increase was found as spermatozoa passed from the proximal to the distal portions of the corpus epididymidis (1·95 compared with 20 spermatozoa bound/egg). Tubules from the proximal epididymis were cultured in conditions which preserved the motility of the contained spermatozoa for 48–72 h. Addition of 2 μm-5α-DHT to the culture medium for 17 h stimulated the incorporation of 3H-labelled amino acids into several protein bands whose mobility in polyacrylamide gel electrophoresis was coincident with those of glycoproteins EP1–EP6, previously identified as androgen-dependent in the hamster epididymis in vivo. Examination of the material extracted from washed spermatozoa with 0·5 m-NaCl revealed the presence of radioactive proteins on spermatozoa. The zona-binding ability of spermatozoa from androgen-treated cultured proximal corpus tubules was significantly increased (P < 0·001) as was the no. of spermatozoa/egg (5·51) compared with the value for control cultures (0·87 spermatozoa/egg).
We suggest that androgen-dependent epididymal secretory proteins that associate with spermatozoa might participate in the formation or activation of a site for zona pellucida recognition in the sperm surface.
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Search for other papers by Patricia S. Cuasnicú in
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Summary. Androgen-dependent epididymal proteins were investigated in the hamster. The stimulation of labelled amino acid incorporation, as well as the colour intensity of bands stained with Coomassie Blue after electrophoresis of the epididymal cytosol from castrated animals with and without androgen replacement, were used as semi-quantitative criteria for evaluation. These techniques allowed the identification of 6 androgen-sensitive bands (EP) with the following relative electrophoretic mobilities with respect to albumin: EP1 = 0·8; EP2 = 1·11; EP3 = 1·21; EP4 = 1·31;EP5 = 1·52; EP6 = 1·63.
The proteins EP1, EP3 and EP4 were also found in fluid from the cauda epididymidis. Extraction of spermatozoa from the distal corpus and cauda epididymidis with 0·25 and 0·5 M-NaCl yielded appreciable amounts of EP2 and EP3 but these bands were not detected in extracts of spermatozoa from proximal segments. The approximate molecular weights were 61 400 for EP1, 42 500 for EP2, 23 800 for EP3, 20 400 for EP4, 26 100 for EP5 and 41 000 for EP6. All bands stained as glycoproteins with periodic acid–Schiff reagent.
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Search for other papers by Fernanda González Echeverría in
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Summary. The increase in zona pellucida binding caused by the exposure of cultured proximal corpus epididymidis to 2 μm-5α-DHT (0·87 and 4·29 spermatozoa/egg for control and 5α-DHT group respectively) was lost when 20 μm-cycloheximide was also added to the medium (0·72 spermatozoa/egg). These results were interpreted as meaning that de-novo protein synthesis was required to obtain the effect of androgens. When a fraction enriched in epididymal glycoproteins EP2–EP6 (18% total protein in epididymal cytosol and 30% in enriched fraction) and depleted of androgens (<120 pg testosterone + DHT/ml) was added to the cultured epididymal tubules, the zona pellucida-binding ability of the contained spermatozoa increased from 0·55 in controls to 2·73 spermatozoa/egg in the extract-treated group (P < 0·02). When the enriched fraction was prepared from epididymides of 30-day castrates, the stimulatory effect was lost (1·04 spermatozoa/egg). We suggest that proteins synthesized in the epididymis are required to obtain the effect of androgens and that the glycoproteins EP2–EP6 may be involved.
Search for other papers by Fernanda González Echeverría in
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Search for other papers by Patricia S. Cuasnicú in
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Summary. The fertility of spermatozoa from the different epididymal segments of hamsters was tested by in-vivo insemination. Caput and proximal corpus spermatozoa were non-fertile; spermatozoa from the distal corpus epididymidis fertilized 13% (38/290) oocytes and those from the proximal and distal cauda epididymidis 71 and 87%, respectively. When tested by in-vitro insemination, distal corpus spermatozoa penetrated 44% of oocytes while those from the distal cauda fertilized 87% of oocytes. Spermatozoa from the distal corpus recovered in Medium BMOC fertilized 13% (28/219) of oocytes in vivo, while those mixed with an epididymal protein preparation (0·8 mg protein/ml) fertilized 24% (49/204; P < 0·01) of oocytes.
When distal corpus spermatozoa were inseminated in vivo with 0·8 mg epididymal protein preparation 34% (31/90) oocytes were fertilized and only 22% (23/103; P < 0·05) oocytes were fertilized when the proteins were obtained from epididymides of animals castrated for 30 days. When distal corpus spermatozoa were preincubated for 5 h in medium without (control) or with protein preparation (0·8 or 1·6 mg protein/ml), a significant increase in in-vitro oocyte penetration was found (25 compared with 45%; P < 0·05) when the protein was present at 1·6 mg/ml.
These results confirm and extend previous observations suggesting a role for androgen-dependent glycoproteins secreted by the epididymis in the acquisition of fertilizing ability that occurs during sperm maturation.
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Summary. Antiserum against rat androgen-dependent secretory epididymal protein DE (raised in rabbit) was added to suspensions of rat spermatozoa from the cauda epididymidis which were used for artificial insemination. While control spermatozoa fertilized 41·6% of oocytes, those exposed to antiserum to protein DE fertilized only 6·6% (P< 0·01). An equal amount of normal rabbit serum (NRS) did not cause inhibition (33·1%). To study the entry of antibodies into the epididymis, caudal tubules were cultured for 24 h and the fertility of the contained spermatozoa was assessed by artificial insemination. Culture in Medium 199 alone or with NRS resulted in spermatozoa which fertilized 52% of oocytes while the presence of antiserum to protein DE in the culture medium yielded spermatozoa which fertilized only 16·6% of oocytes (P < 0·01). These results suggest (1) that the epididymal protein DE might be part of a sperm structure involved in the fertilization process, and (2) that, at least under the present culture conditions, immunoglobulins penetrate the epididymal epithelium in sufficient numbers to reduce fertility significantly.
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Summary. Uptake and metabolism of [3H]testosterone, mainly to 5α-dihydrotestosterone (5α-DHT) and 5α-androstanediol were higher in the caput than in the cauda epididymidis in vitro. The metabolites represented 57, 49 and 47% of the total radioactivity in the caput, corpus and cauda epididymidis, respectively; subcellular distributions of the metabolites in each segment showed 67% of total radioactivity in cytosol and 18% in the nuclei. In both fractions, the amount of 5α-DHT was greater than that of androstanediol while the reverse was true for the mitochondria and microsomes.
The distribution of 5α-reductase activity in subcellular fractions was similar to that of the microsomal marker enzyme NADPH: cytochrome C reductase, whilst 3α-hydroxysteroid dehydrogenase was found mainly in the cytosol. Maximal 5α-reductase activity was at pH 5·3, apparent K m values in the microsomal and nuclear fractions were 1·65 ± 0·7 and 1·75 ± 0·36 × 10−6 m respectively, and the V max in these preparations was 5·28 ± 1·19 and 3·1 ± 0·52 pmol/mg protein/min, respectively. The activity of 5α-reductase was inhibited by Zn2+, Cu2+, Ba2+ and Cd2+ and by epitestosterone, progesterone and 4-androstene-3-one-17β-carboxylic acid.
