Schneider D A, Parks A H, Eades S C, Tackett R L
Department of Large Animal Medicine, University of Georgia, Athens 30602, USA.
Am J Vet Res. 1999 Feb;60(2):233-9.
To compare in vitro smooth muscle relaxation of palmar digital vessels from healthy horses with those from horses in the prodromal stage of experimentally (carbohydrate) induced laminitis.
16 adult horses.
Segments of palmar digital vessels were obtained from 5 healthy horses and 6 horses given carbohydrate. Vascular rings from the palmar digital artery and vein were suspended in individual organ baths containing buffer solution and indomethacin; isometric tension was recorded, and contraction and relaxation were compared. Smooth muscle contraction in response to cumulative addition of phenylephrine was recorded in the absence and presence of 1 microM NG-nitro-L-arginine methyl ester (L -NAME). After wash out, vascular rings were preconstricted with phenylephrine (0.3 microM), and cumulative endothelium-dependent (acetylcholine-induced) and independent (nitroprusside-induced) smooth muscle relaxations were recorded in the absence or presence of L -NAME.
Phenylephrine increased vascular smooth muscle tone in ring preparations of palmar digital arteries and veins. Addition of acetylcholine or nitroprusside induced relaxation of palmar digital artery and vein ring preparations. Use of L-NAME (1 microM) significantly reduced maximal relaxation induced by acetylcholine, but not by nitroprusside. Maximal relaxation induced by acetylcholine, but not by nitroprusside, was reduced in vascular rings prepared from carbohydrate-overloaded horses.
Reduced endothelium-dependent relaxation of palmar digital vessels may have a role in the pathophysiology of acute laminitis after carbohydrate overload in horses.
比较健康马与实验性（碳水化合物诱导）蹄叶炎前驱期马的掌指血管的体外平滑肌舒张情况。
16匹成年马。
从5匹健康马和6匹给予碳水化合物的马获取掌指血管段。将掌指动脉和静脉的血管环悬挂于含有缓冲溶液和吲哚美辛的单个器官浴槽中；记录等长张力，并比较收缩和舒张情况。在不存在和存在1微摩尔N-硝基-L-精氨酸甲酯（L-NAME）的情况下，记录对去氧肾上腺素累积添加的平滑肌收缩情况。冲洗后，用去氧肾上腺素（0.3微摩尔）预收缩血管环，在不存在或存在L-NAME的情况下，记录累积的内皮依赖性（乙酰胆碱诱导）和非依赖性（硝普钠诱导）平滑肌舒张情况。
去氧肾上腺素增加了掌指动脉和静脉环制剂中的血管平滑肌张力。添加乙酰胆碱或硝普钠可诱导掌指动脉和静脉环制剂舒张。使用L-NAME（1微摩尔）显著降低了乙酰胆碱诱导的最大舒张，但不影响硝普钠诱导的最大舒张。在由碳水化合物超载马制备的血管环中，乙酰胆碱诱导的最大舒张降低，但硝普钠诱导的最大舒张未降低。
掌指血管内皮依赖性舒张降低可能在马碳水化合物超载后急性蹄叶炎的病理生理学中起作用。
