Location: Forage-animal Production ResearchTitle: Equine palmar artery, palmar vein and uterine artery express different populations of vasoactive biogenic amine receptors Author
Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract Only
Publication Acceptance Date: 3/8/2013
Publication Date: 7/8/2013
Citation: Hestad, D.A., Mcdowell, K.J., Klotz, J.L. 2013. Equine palmar artery, palmar vein and uterine artery express different populations of vasoactive biogenic amine receptors. J. Anim. Sci. Vol. 91, E-Suppl. 2:566. Interpretive Summary:
Technical Abstract: Consumption of endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum) seed by horses causes constriction of the palmar artery (PA), palmar vein (PV) and reduced blood flow to the corpus luteum that can be measured in vivo by Doppler ultrasonography. In addition, myograph studies demonstrated that some ergot alkaloids, as well as the biogenic amines norepinephrine and 5-hydroxytryptamine, cause constriction of the PA and PV in vitro, but that the PA and PV have different contractile responses to different alkaloids. The objective of this study was to characterize biogenic amine receptors in the PA, PV, and uterine artery (UA) of horses. Immediately after euthanasia, PA, PV and UA were collected from 14 mixed breed mares. In experiment 1, transcriptomes of the PA, PV and UA were analyzed by PCR for presence/absence of adrenergic (ADR), serotonergic (5-HTR), and dopaminergic (DRD) receptor mRNAs (n = 4, 6, and 5 receptor subtypes, respectively). Of those, 2 ADR, five 5-HTR, and 2 DRD receptor subtype mRNAs were consistently expressed. In experiment 2, relative abundance of 5-HTR subtype 1B, 1D, 2A, 2B and 7 mRNAs, as well as GAPDH mRNA, were determined using semi-quantitative real-time PCR. Quantitation of mRNA expression was conducted using the relative standard curve method with expression normalized to GAPDH mRNA. Expression of receptor types differed across vessels (P < 0.0001). Within the PA, 5-HTR2B was more highly expressed (P = 0.03), while other subtypes did not differ. Within the PV, 5-HTR2A had relatively more mRNA than 5-HTR1B (P = 0.01). In the UA, gene 5-HTR2B had the greatest relative quantity of mRNA (P <0.0001), while 5-HT2A had a lower relative quantity of mRNA than 5-HT2B (P < 0.0001) or 5-HT1D (P = 0.0003). Relative differences in vessel receptor types emphasizes the different physiological roles of the vessels under normal physiological conditions. Additionally, different receptor types may also contribute to the different capacities of the vessels to respond to, or be protected from, vasoconstrictive effects of fescue toxicosis in horses.