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Injection of mouse testes with aspermatogenic substance (AS) isolated from bull seminal vesicle fluid inhibited sperm production and caused a decrease in the weight of the testes. Subcutaneous injections of AS also caused a decrease in testis weight, but spermatogenesis was only slightly affected.Administration of AS (2 to 2·5 mg) to female mice 1 to 13 days after mating resulted in a highly significant decrease in the number of embryos. When concentrations of 12·5 μg AS/ml, or more, were present in the medium in which two-blastomere mouse embryos were incubated, further development was arrested in 100% of the embryos. Invivo, however, death of the embryos occurred only after nidation. Injection of AS into prepubertal males or females did not provoke any visible disturbances at the time, or later when sexual maturity was reached.The presence of AS in the diluent had no effect on the sperm motility or sperm survival time of bull, ram, boar and rabbit spermatozoa or on the fructolysis of bull and ram spermatozoa.Samples of AS showed no proteolytic, DNase, esterase, alkaline phosphatase, acid phosphatase or lactate dehydrogenase activities but had high RNase activity and AS was therefore named AS RNase. Incorporation of [2-14C]orotic acid into male mice injected with AS RNase made it possible to detect a significant reversible decrease of pyrimidine synthesis in testicular tissue. No decrease of RNA in liver and kidney tissue could be detected.

Aspermatogenic substance (AS) was isolated from bull seminal vesicle fluid by precipitation with acetic acid and ammonium sulphate, and subjected to CM Sephadex C-50 and Sephadex G-100 column chromatography. The molecular weight of the monomer of AS was 22,000 and of the dimer was 44,000 as determined by gel filtration. The purity of the AS was controlled by disc electrophoresis in acrylamide gel, starch-gel electrophoresis, immunoelectrophoresis in agar gel, by peak homogeneity at the last step of separation and by the ultracentrifugation pattern. The N-terminal amino acid was lysine. The absorbance of 0·1% AS at 280 nm in pH 5·5 buffer was 0·510. The svalue obtained for 0·5% AS solution was 2·7.

The protein spectrum of boar seminal plasma is formed mainly by the seminal vesicle fluid proteins, and to a lesser extent by the proteins in the fluids of the cauda epididymidis and prostate.The proteins of the seminal plasma, the fluids of the cauda epididymidis, prostate, seminal vesicles and the blood serum were divided into five peaks by column chromatography on Sephadex G-100. The proteins of Peak I in boar seminal plasma (mol. wt at least 150,000) were mostly derived from the seminal vesicle fluid and to a small extent from the fluids of the cauda epididymidis and prostate. The proteins of Peak II (mol. wt 120,000) were found in the blood serum only, and those of Peak III (mol. wt 69,000) in the seminal vesicle fluid, the fluid of the cauda epididymidis and the prostate. Peak IV (mol. wt 34,000) was formed by proteins originating mainly from the seminal vesicles and partly from the prostate. The proteins of Peak V (mol. wt 12,000 to 14,000) were derived from the fluids of the cauda epididymidis and the prostate.These conclusions were confirmed by comparing the activity of acid and alkaline phosphatase and esterase by means of disc electrophoresis on polyacrylamide gel at pH 9·4 and 4·3 and by immunoelectrophoresis of all the fluids and fractions obtained by column chromatography of proteins on Sephadex G-100.

Damage to spermatogenesis in mice, rats, guinea-pigs, rabbits and rams after the intramuscular or subcutaneous administration of bull seminal vesicle fluid was reported by Matoušek (1966, 1969). Matoušek & Petrovská (1969) also observed an inhibitory effect of bull seminal vesicle fluid on the fertility of female mice and hens. The present report deals with the separation and purification of a substance that causes aspermatogenesis in mice.Seminal vesicle fluid obtained from mature bulls at slaughter was diluted 2·5-fold with 2% acetic acid and mixed for 30 min at room temperature. The precipitate was separated from the supernatant fluid by centrifugation at 7000 gfor 45 min. The aspermatogenic substance remained in the supernatant fluid. The bulk of the protein was then precipitated by 3 m-ammonium sulphate and separated from the supernatant by further