PS5-18. Exploratory Assessment of Dopamine Infusion Effects on Endogenous Equine Insulin Secretion During Oral Sugar and Tissue Sensitivity Testing.

Abstract Insulin dysregulation (ID) increases the risk for hyperinsulinemia-associated laminitis. While limited in the horse, dopaminergic modulation of insulin has been observed in other species. Seven mature horses (14 ± 4 years; 517 ± 52 kg) classified as healthy (H; n = 3), ID (n = 2), or pituitary pars intermedia dysfunction (PPID; n = 2) were enrolled in a crossover study. Each horse completed a standard oral sugar test (OST) and Euglycemic Hyperinsulinemic Clamp EHC (EHC; insulin 3 mU/kg/min) followed by OST and EHC with concurrent dopamine hydrochloride (DA) infusion (2.5 µg/kg/min) with a 1-week washout between tests. Data are presented descriptively as individual values and median (interquartile range) to illustrate distributional patterns and variability. Interpretation focused on the magnitude and direction of responses to inform effect size estimation in this pilot dataset. Overall, dopamine infusion did not meaningfully alter insulin-mediated glucose utilization during the EHC, while modest shifts in OST responses suggest potential dose- or context-dependent effects that warrant further investigation in larger studies.