Effects of an endothelin receptor antagonist and nitroglycerin on digital vascular function in horses during the prodromal stages of carbohydrate overload-induced laminitis.
OBJECTIVE
To evaluate changes in digital vascular function in horses with carbohydrate overload (CHO)-induced laminitis and determine the effects of an endothelin (ET) receptor antagonist and nitroglycerin on laminitis-associated vascular dysfunction.


METHODS
20 adult horses without abnormalities of the digit.


METHODS
Hemodynamic variables were recorded before (baseline) and hourly after all horses were administered a CHO ration via nasogastric tube. In 4 groups of 5 horses each, saline (0.9% NaCl) solution or ET receptor antagonist (10(5)M in digital blood) was administered into the digital arterial circulation according to 1 of 2 schedules. During anesthesia, blood flow; arterial, venous, and capillary pressures; and total, precapillary, and postcapillary resistances were measured in an isolated perfused digit of each horse. In all groups, nitroglycerin was infused (10(5)M in digital blood), and digital microvascular assessments were repeated.


RESULTS
The CHO caused a significant decrease in right atrial pressure by 14 hours that was not affected by administration of saline solution or ET receptor antagonist. In isolated digits of anesthetized horses, CHO resulted in a significant decrease in digital blood flow associated with a significant increase in total and postcapillary resistances. Treatment with the ET receptor antagonist and nitroglycerin caused a significant decrease in total resistance. Postcapillary resistance was significantly decreased following treatment with the ET receptor antagonist but was not altered by treatment with nitroglycerin.


CONCLUSIONS
Treatment with an ET receptor antagonist and nitroglycerin resulted in significant improvement in vascular resistance in isolated perfused digits of anesthetized horses with CHO-induced laminitis.
Eades
Susan C
SC
Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, 70803, USA.
Stokes
Ashley M
AM
Moore
Rustin M
RM
D000821:Animal Feed; D000818:Animals; D002241:Carbohydrates / Q000008:administration & dosage / Q000009:adverse effects*; D065128:Endothelin Receptor Antagonists; D005528:Foot / Q000098:blood supply; D005534:Foot Diseases / Q000139:chemically induced / Q000662:veterinary*; D006734:Horse Diseases / Q000139:chemically induced / Q000188:drug therapy* / Q000473:pathology; D006736:Horses / Q000502:physiology; D005996:Nitroglycerin / Q000494:pharmacology* / Q000627:therapeutic use; D009842:Oligopeptides / Q000494:pharmacology* / Q000627:therapeutic use; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology / Q000627:therapeutic use
D002241:Carbohydrates; D065128:Endothelin Receptor Antagonists; D009842:Oligopeptides; D014665:Vasodilator Agents; C082887:PD 145065; D005996:Nitroglycerin