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Serial alterations in digital hemodynamics and endothelin-1 immunoreactivity, platelet-neutrophil aggregation, and concentrations of nitric oxide, insulin, and glucose in blood obtained from horses following carbohydrate overload

Susan C. Eades DVM, PhD1, Ashley M. Stokes DVM, PhD2, Philip J. Johnson BVSc, MS3, Casey J. LeBlanc DVM, PhD4, Venkataseshu K. Ganjam BVSc, PhD5, Preston R. Buff PhD6, and Rustin M. Moore DVM, PhD7
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  • 1 Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.
  • | 2 Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.
  • | 3 Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211.
  • | 4 Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.
  • | 5 Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211.
  • | 6 Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211.
  • | 7 Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.

Abstract

Objective—To quantify changes in endothelium-derived factors and relate those changes to various aspects of digital hemodynamics during the prodromal stages of carbohydrate overload (CHO)-induced laminitis in horses.

Animals—20 adult horses without abnormalities of the digit.

Procedures—Digital and jugular venous blood samples were collected at 1-hour intervals (for assessment of endothelin-1 [ET-1] immunoreactivity and measurement of glucose, insulin, and nitric oxide [NO] concentrations) or 4-hour intervals (CBC and platelet-neutrophil aggregate assessment) for 8 hours or 16 hours after induction of CHO-associated laminitis in horses treated with an ET-1 antagonist. Effects of treatment, collection site, and time and the random effects of horse on each variable were analyzed by use of a repeated-measures model. Where treatment and collection site had no significant effect, data were combined.

Results—Compared with baseline values, CHO resulted in changes in several variables, including a significant increase from baseline in digital blood ET-like immunoreactivity at 11 hours; digital blood ET-like immunoreactivity was significantly greater than that in jugular venous blood at 8, 9, 11, and 12 hours. Digital and jugular venous blood concentrations of glucose increased from baseline significantly at 3, 4, and 5 hours; insulin concentration increased significantly at 5 hours; and the number of platelet-neutrophil aggregates increased significantly at 12 hours.

Conclusions and Clinical Relevance—In horses, concurrent increases in venous blood ET-1 immunoreactivity, insulin and glucose concentrations, and platelet-neutrophil aggregates support a role of endothelial dysfunction in the pathogenesis of CHO-induced laminitis.

Contributor Notes

Dr. LeBlanc's present address is Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

Supported by a grant from the USDA National Research Initiative.

The authors thank Michael Keowen, Catherine Koch, and Frank Garza for technical assistance.

Address correspondence to Dr. Eades.