Development of an intra-lamellar microdialysis method for laminitis investigations in horses

Microdialysis (MD) was used for continuous monitoring of the lamellar extracellular fluid (ECF) in six mature healthy Standardbred horses. MD probes were introduced into the lamellar tissue under local anaesthesia. Following intravenous injection of gentamicin (5mg/kg), MD and serum samples were collected for 24h and analysed using a sensitive ELISA test for gentamicin and fluorescence polarization immunoassay for urea concentrations. Calibration of probes was performed through in vivo urea recovery and in vitro gentamicin and urea recovery. Data obtained from different body compartments were compared statistically. The concentration of gentamicin was significantly higher in serum than lamellar ECF for the first 8h (P<0.05), but remained above the minimum inhibitory concentration (MIC) in the ECF for a further 4h. The method will be useful to monitor changes in the lamellar ECF during laminitis and the local kinetics of drugs used therapeutically for this condition.