Comparison by three different radioimmunoassay systems of the polymorphism of plasma FSH in mares in various reproductive states.

The study measured the polymorphism of the follicle stimulating hormone (FSH) in mares in various reproductive states using three different antibodies in radioimmunoassay systems. The research suggests that the forms of FSH in the blood can vary and this variance might have significant functional consequences.

Purpose and Methodology of the Research

• The aim of the study was to understand the polymorphism (multiple forms) of follicle-stimulating hormone (FSH) in the plasma of mares in different reproductive states.
• The researchers used three different radioimmunoassay systems, each based on a different antibody identified as ‘o’, ‘h’, and ‘e’, to analyze the FSH levels from mares.
• FSH levels were measured in pituitary, pituitary venous, and jugular blood, and samples were collected regularly from the mares.

Findings from the Study

• In the pituitary, four forms of FSH were identified having different isoelectric points (the pH at which a particular molecule or compound carries no net electrical charge) and relative potency across the three assays.
• The mean FSH concentrations and the short-term patterns in the jugular blood were dependent on the assay used and the reproductive state of the mare.
• Pituitary venous blood showed an elevation in FSH concentrations above the jugular values; however, the relationship among the three assays remained consistent.
• The study confirmed the pulsatility (pulse variation) of FSH secretion at estrus (a period of sexual receptivity in female animals) which could only be observed in pituitary blood.

Implications of the Study

• The outcomes suggest that FSH in plasma is polymorphic, showing different forms, and the changes in the circulating form of the hormone may have a functional significance.
• The polymorphism of FSH also affects its immunoactivity, which means that its ability to provoke an immune response varies with its form.
• The results pose a challenge when selecting a radioimmunoassay for clinical or research use since further FSH structure-function studies are needed to determine which form of the hormone should be measured in each specific situation.