Determination of serotonergic receptor profiles in equine palmar artery and vein and uterine artery

Authors: Klotz, James

Submitted to: Ruminant Physiology International Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/24/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Cattle can be exposed to ergot alkaloids through fungal contamination of feed and forage that can result in severe reductions in productivity. Previous work has demonstrated that exposure to ergot alkaloids like ergovaline cause vasoconstriction in peripheral and visceral vasculature primarily through serotonin receptor 5HT2A. Currently, effects ergot alkaloids have on receptor signaling are not fully understood and ergopeptides interaction with vascular receptors that regulate smooth muscle contraction could alter serotonin receptors leading to observed decreases in vascular reactivity. Objectives of this study were to determine if exposure of bovine lateral saphenous veins to ergovaline, 5HT2A antagonist, inhibitors of phospholipase C and protein kinase C will alter the vasoactivity to serotonin and the concentration of 5HT2A receptors. Lateral saphenous veins were collected from Holstein steers (n = 8; kg) at a local abattoir. Blood vessels were cleaned of external adipose and connective tissues and sliced in 2-mm cross sections. Cross-sections were incubated for either 2 hr or 24 hr in oxygenated Krebs-Henseleit buffer (95%O2/5%CO2; pH=7.4; 37'C) containing 1 x 10- 6 M of either a vehicle (Control), ketanserin (KET; 5HT2A receptor antagonist), 1-[6-[[(17ß)-3-Methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (PLC-; phospholipase C inhibitor), 2-[1-(3-Dimethylaminopropyl)indol-3-yl]-3-(indol-3-yl) maleimide (PKC-; protein kinase C inhibitor), or ergovaline (ergopeptide alkaloid). Following the incubation, blood vessel cross-sections were either mounted in a multi-myograph or ground in liquid N, homogenized in a protein extraction buffer, and frozen for later 5HT2A receptor protein quantification with a 5HT2A ELISA. Cross-sections in the myograph were exposed to increasing concentrations of serotonin. Contractility data were normalized as percent contractile response induced by a reference addition of 1 x 10- 4 M norepinephrine and both the contractile response and the protein expression data were analyzed as a completely randomized design using SAS for effects of incubation treatment and incubation time. Veins that were incubated for 2 hr and 24 hr with KET, PLC-, and PKC- all had similar response curves that did not differ from the Control vein responses (P > 0.05). Veins exposed to ERV for 2 hr and 24 hr did not respond to increasing concentrations of serotonin and differed from Control veins and all compounds evaluated for both incubation intervals (P < 0.05). There were no effects of incubation treatment or time on the quantity of 5HT2A receptor protein. These results indicate ergovaline-derived effects on 5HT2A receptor function occur by means other than receptor number or interrupting signaling pathways associated with smooth muscle contraction.