Hyaluronan in horses: physiological production rate, plasma and synovial fluid concentrations in control conditions and following sodium hyaluronate administration.

The research article mainly explores the physiological production rate, plasma, and synovial fluid concentrations of Hyaluronan (Hyaluronic acid) in horses under normal conditions and after administration of sodium hyaluronate, aiming to establish a useful guideline for medication control in horse racing.

Objective summary

The main objective of this study was to understand the behavior of Hyaluronic acid (HA), a naturally occurring substance used in treating joint diseases in horses after its administration. The researchers sought to establish the normal plasma HA concentrations in racing horses, determine the endogenous production rate of HA, and document how the substance behaves when administered intravenously or directly into the joint using recommended therapeutic doses.

Methods

• The researchers measured Hyaluronan concentrations in the plasma using a specific test called ELISA (Enzyme-Linked Immunosorbent Assay).
• The concentrations in synovial fluid (a viscous, non-Newtonian fluid found in the cavities of synovial joints) were determined using a radiometric binding assay, a scientific procedure used to measure the affinity and number of ligand-binding sites.

Results

• The mean plasma HA concentration in 120 horses after competitions was found to be 89 ng/ml.
• In six experimental horses, the synovial fluid’s control concentration was 328+/-112 microg/ml.
• After the administration of sodium hyaluronate (37.8 mg in total) intravenously, it was observed that the terminal half-life was very short ( approximately 43 +/- 29 minutes) and the plasma concentration returned to control values after a delay of three hours.
• The endogenous HA production rate was found to be 33-164 mg in total per day. This is about 1-4 times the recommended daily intravenous dose.
• Twenty-four hours after intra-articular administration, the HA concentration was not significantly different from control values (328+/-112 microg/ml).

Conclusions

Based on the results, the researchers concluded that due to HA’s rapid disappearance from plasma after intravenous administration and from the joint after intra-articular administration, a more appropriate approach needs to be developed for long-term detection. This understanding is important for establishing a medication control policy in horse racing, ensuring that HA is being used responsibly and the health of racehorses is not compromised.