Hypotaurine in the Reproductive Tract

Abstract

Hypotaurine was first detected in boar semen (Horst and Grooten, 1966). The free amino acid composition of boar seminal plasma was examined by paper electrophoresis at pH 4.5 and at pH 1.9 followed by ascending chromatography in the solvent system butanol-acetic acid-water (12:3:5). The amino acids were detected with ninhydrin. Leucine, phenylalanine, valine, alanine, glycine, serine and glutamic acid were present in readily detectable amounts; basic amino acids were only found in very small quantities. The most striking phenomenon, however, was a very large spot of an amino acid, which after electrophoresis at pH 4.5 appeared in the neutral fraction approximately in the same position as glycine, but, after electrophoresis at pH 1.9, the spot was found far to the left of glycine and of glutamic acid. This showed that the unknown amino acid would contain, besides the amino group, an acidic group stronger than the carboxyl group as e.g. a sulfonic acid group. Micro reactions according to Feigl (1960) established the presence of sulfur containing groups. Also thanks to the report of the chromatographic behaviour of eight sulfur containing amino acids, all related to cysteine, given by Italian investigators (De Marco et al., 1965) we were able to show that the unknown amino acid was hypotaurine. Later on the presence of hypotaurine in boar semen and in semen of other species of animals has been confirmed by other investigators (among others Johnson, 1972 and Kochakian, 1973).