USDA-ARS, Forage-Animal Production Research Unit, Lexington, KY 40546-0091, USA.
J Anim Sci. 2011 Jun;89(6):1944-51. doi: 10.2527/jas.2010-3532. Epub 2011 Feb 4.
Endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum) produces ergot alkaloids that are associated with peripheral vasoconstriction in grazing animals, and ingestion of these alkaloids may affect splanchnic vasculature. Peripheral effects of ergot alkaloids have been well documented previously in cattle using a lateral saphenous vein bioassay. Because of significant differences in morphological and functional characteristics between vasculature supporting digestive and peripheral tissues, the bovine foregut vascular model required validation. Experiments were conducted, using dose-responses to norepinephrine and serotonin that were normalized to either 0.12 M KCl, or 0.1 mM norepinephrine or serotonin, to compare responses of vessels equilibrated at different tensions on the day of collection or the day after collection. Segments of a branch of right ruminal artery and vein were collected from the ventral coronary groove of healthy cattle of mixed breed, age, and sex (n = 20) at local abattoirs. Cross-sections of the artery and vein were suspended on luminal supports in a chamber of a multimyograph containing continuously oxygenated Krebs-Henseleit buffer (95% O(2)/5% CO(2), pH 7.4; 37°C). Vessels were allowed to equilibrate at either 0.5 or 1.0 g of tension for 1.5 h before exposure to a reference compound. Increasing concentrations of each biogenic amine were administered in 15-min intervals after buffer replacement. Data were normalized as a percentage of the contractile response induced by the reference compound for each tension and day of analysis. The ruminal artery and vein were both more responsive to KCl as a reference compound (P < 0.05) than to norepinephrine or serotonin and did not differ between days when normalized with KCl. Ruminal arteries had greater contractile responses (P < 0.05) when tension was set to 1.0 g, compared with 0.5 g, during equilibration. The ruminal vein response had a more stable maintenance of baseline tension in vessels equilibrated at 0.5 g of resting tension. Development of this bioassay allows separation of the effects tall fescue alkaloids exert on both the right ruminal artery and vein as representative vessels that service tissues functioning in nutrient absorption.
内生真菌感染（Neotyphodium coenophialum）高羊茅（Lolium arundinaceum）产生麦角生物碱，与放牧动物的外周血管收缩有关，这些生物碱的摄入可能会影响内脏血管。以前已经使用外侧隐静脉生物测定法在牛中很好地记录了麦角生物碱的外周作用。由于支持消化和外周组织的血管在形态和功能特征上存在显著差异，因此需要验证牛前胃血管模型。使用对去甲肾上腺素和 5-羟色胺的剂量反应进行了实验，这些反应均以 0.12 M KCl 或 0.1 mM 去甲肾上腺素或 5-羟色胺归一化，以比较在收集当天或收集后一天平衡在不同张力下的血管的反应。从混合品种、年龄和性别的健康牛的腹冠状沟收集右瘤胃动脉和静脉的分支段（n = 20）在当地屠宰场。动脉和静脉的横截面悬挂在多肌描记器腔中的腔室内，该腔室含有连续充氧的 Krebs-Henseleit 缓冲液（95% O 2 / 5% CO 2 ，pH 7.4；37°C）。在暴露于参考化合物之前，将血管在 0.5 或 1.0 g 的张力下平衡 1.5 小时。在缓冲液替换后 15 分钟的间隔内给予每种生物胺的递增浓度。数据作为每个张力和分析日参考化合物诱导的收缩反应的百分比进行归一化。与去甲肾上腺素或 5-羟色胺相比，瘤胃动脉和静脉对 KCl 作为参考化合物的反应都更强（P <0.05），并且在 KCl 归一化时没有差异。与 0.5 g 时相比，当张力设置为 1.0 g 时，瘤胃动脉的收缩反应更大（P <0.05）。在 0.5 g 静息张力下平衡时，瘤胃静脉的反应具有更稳定的基线张力维持。该生物测定法的开发允许分离内生真菌生物碱对代表参与营养吸收的组织的右瘤胃动脉和静脉的作用。
