Protein composition of seminal plasma in fractionated stallion ejaculates.

The research article focuses on analyzing the protein composition of different ejaculate fractions from stallions, both normal and subfertile. With the use of advanced techniques like mass spectrometry and reverse-phase liquid chromatography, the researchers found no significant differences in the protein composition across various ejaculate fractions and no correlation between the specific proteins and sperm motility.

Objectives and Methods Used in the Research

• The main purpose of the research was to understand the protein composition of different fractions of a stallion’s ejaculate. This involved collecting fractionated ejaculates from two normal and two subfertile stallions. The fractions examined included pre-sperm fluid, first sperm-rich jets, main sperm-rich portion, sperm-poor jets, and a combined whole-ejaculate sample.
• The researchers utilized techniques like mass spectrometry and reverse-phase liquid chromatography for an in-depth examination of the protein composition in the different ejaculate fractions. N-terminal sequencing was employed to identify the proteins present, and the proteins within the fractions were quantitatively compared using the area-under-the-curve (AUC) method.
• Another aspect of the study involved collecting semen samples from seven stallions. The collected samples representing fractions with the highest and lowest sperm concentrations and whole ejaculate samples were examined using SDS-PAGE and densitometry.

Findings from the Research

• The researchers did not find any significant differences in the AUC-values of the Horse Seminal Protein-1 (HSP-1) and Horse Seminal Protein-2 (HSP-2) peaks, or the peak containing Horse Seminal Protein-3 and Horse Seminal Protein-4 (HSP-3/4) across the various ejaculate fractions studied.
• The levels of HSP-1, HSP-2, and HSP-3/4 were not correlated with total sperm motility, progressive sperm motility, or average path velocity after storage.
• In the first part of the trial, the research did not find any significant differences between the amount of different protein groups in the seminal plasma across different ejaculate fractions. However, in the second part of the trial, the researchers noticed that proteins in the 60-70 kDa range were more abundant in the fraction with low sperm concentration as compared to the fraction with high sperm concentration and the whole ejaculate sample. This suggested that these proteins primarily came from the seminal vesicles, which produced most of the seminal plasma in the fraction with low sperm concentration.