Evaluation of the possible role of prostaglandin F(2 alpha) in laminitis induced in horses by nasogastric administration of black walnut heartwood extract.
OBJECTIVE
To provide insights into the role of prostaglandin F(2 alpha) (PGF(2 alpha)) in the developmental stages of laminitis induced in horses by ingestion of black walnut heartwood extract (BWHE).


METHODS
10 adult mixed-breed horses.


METHODS
Horses were separated into 2 groups and were euthanatized at 12 hours after placebo (water) administration (control horses) or after BWHE administration and development of Obel grade 1 laminitis. Blood samples were obtained to determine plasma PGF(2 alpha) concentrations hourly for the first 4 hours and subsequently every 2 hours after substance administration. Laminar arteries and veins were isolated, and responses to increasing concentrations of PGF(2 alpha) were measured before and after preincubation of blood vessels with prostanoid and thromboxane receptor antagonists SQ 29,548, SC-19220, and AH 6809.


RESULTS
Plasma PGF(2 alpha) concentrations increased in horses given BWHE; the WBC count decreased concurrently. In control horses, PGF(2 alpha) was a potent contractile agonist for laminar veins but not for laminar arteries. In horses given BWHE, PGF(2 alpha) was similarly selective for laminar veins; however, the magnitude of PGF(2 alpha)-induced venoconstriction was less than that in control horses. After preincubation with SQ 29,548, laminar veins from control horses responded to PGF(2 alpha) with a small degree of dilation, whereas laminar veins from horses given BWHE did not.


CONCLUSIONS
PGF(2 alpha) may play a role in the inflammatory and vascular dysfunction associated with the prodromal stages of laminitis. Prostanoids such as PGF(2 alpha) may be viable targets for the prevention of acute laminitis in horses.
Noschka
Erik
E
Department of Large Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA 24071, USA.
Moore
James N
JN
Peroni
John F
JF
Lewis
Tristan H
TH
Lewis
Stephen J
SJ
Robertson
Tom P
TP
D000818:Animals; D001158:Arteries / Q000187:drug effects; D015237:Dinoprost / Q000378:metabolism*; D005534:Foot Diseases / Q000139:chemically induced / Q000378:metabolism / Q000662:veterinary*; D006724:Hoof and Claw / Q000098:blood supply / Q000378:metabolism / Q000473:pathology*; D006734:Horse Diseases / Q000139:chemically induced* / Q000378:metabolism; D006736:Horses; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism / Q000662:veterinary*; D007441:Intubation, Gastrointestinal; D031324:Juglans / Q000737:chemistry; D007794:Lameness, Animal / Q000139:chemically induced; D010656:Phenylephrine; D010936:Plant Extracts / Q000008:administration & dosage / Q000633:toxicity*; D014680:Veins / Q000187:drug effects; D014934:Wood / Q000737:chemistry
D010936:Plant Extracts; D010656:Phenylephrine; D015237:Dinoprost