Haefliger I O, Flammer J, Lüscher T F
Department of Ophthalmology, University Hospitals, Basel, Switzerland.
Invest Ophthalmol Vis Sci. 1993 Apr;34(5):1722-30.
Endothelial cells modulate vascular tone by releasing the vasodilator nitric oxide (NO) or the vasoconstrictor endothelin-1. From one vascular bed to another and between vessels of different diameter, heterogeneities of endothelium-dependent regulatory mechanisms exist. Hence, the current study compared the effects of NO and endothelin-1 in the porcine ophthalmic artery and one of its branches, the ciliary artery.
Porcine eyes were obtained at the slaughterhouse. The ophthalmic and ciliary arteries were dissected free under a microscope and suspended in myograph systems (95% O2 and 5% CO2, 37 degrees C) for isometric tension recording.
In both vessels, bradykinin stimulated the release of NO, but the sensitivity to bradykinin increased with decreasing vascular diameter. By contrast, the basal release of NO became less efficient in inhibiting contractions to serotonin and endothelin-1 in ciliary versus ophthalmic artery. Endothelin-1 induced potent contractions that were more pronounced in ciliary than in ophthalmic artery. Serotonin-induced contractions also were more efficient in ciliary artery but less than to those to endothelin-1. Contractions to serotonin were inhibited in both blood vessels by the 5-HT2 serotonergic antagonist ketanserin.
Thus endothelium-derived vasoactive substances are potent regulators of porcine extraocular ophthalmic circulation. Their effects increase with decreasing vascular diameter, suggesting an important role of NO and endothelin-1 in the regulation of ophthalmic circulation. A dysfunction of these regulatory mechanisms could have implications about the pathogenesis of ophthalmic complications seen in diabetes, hypertension, and in certain forms of glaucoma associated with ocular vasospasms.
内皮细胞通过释放血管舒张剂一氧化氮（NO）或血管收缩剂内皮素-1来调节血管张力。从一个血管床到另一个血管床以及不同直径的血管之间，存在内皮依赖性调节机制的异质性。因此，本研究比较了NO和内皮素-1在猪眼动脉及其分支之一睫状动脉中的作用。
在屠宰场获取猪眼。在显微镜下将眼动脉和睫状动脉分离出来，并悬挂在肌动描记系统中（95% O₂和5% CO₂，37℃）以记录等长张力。
在这两种血管中，缓激肽均刺激NO的释放，但对缓激肽的敏感性随血管直径减小而增加。相比之下，在睫状动脉中，NO的基础释放对抑制血清素和内皮素-1引起的收缩作用效率较低，而在眼动脉中则较高。内皮素-1诱导的强烈收缩在睫状动脉中比在眼动脉中更明显。血清素诱导的收缩在睫状动脉中也更有效，但比内皮素-1诱导的收缩作用弱。5-HT₂血清素能拮抗剂酮色林可抑制这两种血管中血清素诱导的收缩。
因此，内皮源性血管活性物质是猪眼外眼循环的有效调节因子。它们的作用随血管直径减小而增强，表明NO和内皮素-1在眼循环调节中起重要作用。这些调节机制的功能障碍可能与糖尿病、高血压以及某些与眼部血管痉挛相关的青光眼形式中出现的眼部并发症的发病机制有关。
