Measurement of free cortisol and the capacity and association constant of cortisol-binding proteins in plasma of foals and adult horses.

This research article investigates the ability of cortisol-binding proteins in horses to bind cortisol, a hormone. The researchers developed a method to measure these proteins in the horse and noticed differences in this process when compared to other species.

Research Methodology and Objective

• The main objective of the study was to devise a direct method to measure the capacity of the high-affinity binding protein, cortisol-binding globulin (CBG), for use in horses.
• Researchers also sought to isolate unique aspects of cortisol binding in horses in comparison to other species.

Findings

• The study found that the CBG content in the plasma of newborn horses was the lowest observed among any other species studied.
• Remarkably, the concentration of CBG in the horse’s system was found to increase with age, a characteristic opposing the trend seen in other species where it typically diminishes.

New Bindings Discovered

• Interestingly, it was observed that the plasma of newborn foals contains a binding protein not previously reported in other species. This protein was found to bind an equivalent amount of cortisol as does CBG.
• This newly-discovered protein exhibits a binding capacity and affinity that are midway between that of albumin and CBG.
• The researchers hypothesized that this protein may play a crucial role in prenatal and postnatal phases.
• In the prenatal phase, this protein might assist in enhancing the transfer of cortisol from the mother to the fetus.
• In contrast, in the postnatal phase, it may help mitigate the impacts of the significant increase in cortisol release associated with the stress of birth.