STUDIES OF FREE AMINO ACIDS IN NORMAL AND STERILE HUMAN SEMEN

Abstract

Twenty-eight free amino acids in human semen, which were stood at room temperature (20-25°C) for 3 hours after ejaculation, were analysed both qualitatively and quantitatively in an automatic amino acid analyzer (JLC-5AH). In order to clearly separate Asparagine and Glutamine, lithium citrate buffer's method was used for the analysis of acidic and neutral amino acids.
The ninety-five samples were divided to following 4 groups, 1. fertile, 2. subfertile, 3. infertile and 4. azoospermic groups. Group 1, 2 and 3 were classified according to the sperm counts and sperm motility.
Low contents of almost all amino acids seemed to be demonstrated in the subfertile, infertile and azoospermic groups, comparing with the fertile group. The contents of amino acids between the fertile group and the other 3 groups were significantly different (p.<0.01-0.05), particularly in the contents of Lysine, Aspartic acid, Glutamic acid, Glycine, Alanine, Valine and Phenylalanine. But Asparagine and Glutamine showed almost the same amounts of amino acids in all groups. In addition, Citrulline showed a high content in the azoospermic group than in the non-azoospermic groups.
Seven samples were studied for successive changes in free amino acid contents. The total contents of amino acids in 2 healthy cases increased rapidly within 3 hours after ejaculation and moderately thereafter. In contrast, amino acid contents in 3 cases with sterility increased after 3 hours. In one case with azoospermia, a very rapid increase of amino acid contents was observed during initial a few hours, but no increase was observed after 3 hours. In a vasectomized case, although amino acid contents were quantitatively low, the increasing rate was very steep and constant.
Thus, amino acid contents in normal human semen should increase rapidly in initial a few hours after ejaculation, suggesting that spermatozoa may be protected by these amino acids during penetration through the female genital tract. The low content of free amino acids obtained in initial a few hours after ejaculation in cases with oligozoospermia may play a role in the cause of infertility.