The effect of tumour necrosis factor-α and insulin on equine digital blood vessel function in vitro.
OBJECTIVE
Insulin and inflammatory cytokines may be involved in equine laminitis, which might be associated with digital vascular dysfunction. This study determined the effects of TNF-α and insulin on the endothelial-dependent relaxant responses of equine digital blood vessels and on equine digital vein endothelial cell (EDVEC) cGMP production.


METHODS
Isolated rings of equine digital arteries (EDAs) and veins (EDVs) were obtained and EDVECs were cultured from horses euthanized at an abattoir.


METHODS
The effect of incubation with TNF-α (10 ng/ml) and/or insulin (1,000 μIU/ml) for 1.5 h or overnight under hyperoxic and hypoxic conditions on carbachol (endothelium-dependent) induced relaxation was assessed. The time course and concentration dependency of the effect of TNF-α and the effect of insulin (1,000 μIU/ml) on EDVEC cGMP production was determined.


RESULTS
Incubation of EDAs overnight with TNF-α under hypoxic conditions resulted in endothelial-dependent vascular dysfunction. EDVs produced a more variable response. TNF-α increased EDVEC cGMP formation in a time- and concentration-dependent manner. Insulin had no significant effects.


CONCLUSIONS
There is a mismatch between the results obtained from isolated vessel rings and cultured endothelial cells suggesting TNF-α may reduce the biological effect of NO by reducing its bioavailability rather than its formation, leading to endothelial cell dysregulation.
Royal Veterinary College, London, UK, nmenziesgow@rvc.ac.uk.
Nicola J
NJ
Menzies-Gow
H
H
Wray
S R
SR
Bailey
P A
PA
Harris
J
J
Elliott
D000818:Animals; D001158:Arteries / Q000187:drug effects* / Q000502:physiology; D002217:Carbachol; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D006736:Horses; D018496:Hyperoxia / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D008683:Metatarsophalangeal Joint; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects; D014680:Veins / Q000187:drug effects* / Q000502:physiology
D007328:Insulin; D014409:Tumor Necrosis Factor-alpha; D002217:Carbachol; D006152:Cyclic GMP