Haefliger I O, Flammer J, Lüscher T F
Department of Ophthalmology, University Hospitals, Basel, Switzerland.
Invest Ophthalmol Vis Sci. 1992 Jun;33(7):2340-3.
The vascular endothelial cells have the ability to modulate local vascular tone by releasing relaxing factors such as nitric oxide or the vasoconstrictor peptide endothelin-1. Although this regulatory system is found in all vertebrates, there is a great heterogeneity in the release of these endothelium-derived substances, from one organ to an other, between large and small vessels, and between different species. Therefore, observations made in certain vascular beds or animals do not necessarily apply to human ophthalmic circulation. The present study was designed to investigate endothelial mediators in the human ophthalmic artery. The results show that in the human ophthalmic artery, nitric oxide is released under basal conditions and that its production can be markedly stimulated by bradykinin, acetylcholine, and particularly histamine, which cause profound vascular relaxation. In contrast, endothelin-1 evoked potent contractions, which were unaffected by the calcium antagonist nifedipine. However, upon re-exposure of the blood vessels to the peptide, marked tachyphylaxis occurred. These findings demonstrate that in the human ophthalmic artery, endothelium-derived nitric oxide and endothelin are very potent modulators of vascular tone, suggesting that they play an important role in the regulation of local blood flow in the eye. Hence, endothelium dysfunction may represent a new pathogenetic mechanism in disease states associated with altered blood flow to the eye, such as diabetes, hypertension, and some forms of low-tension glaucoma.
血管内皮细胞能够通过释放一氧化氮等舒张因子或血管收缩肽内皮素-1来调节局部血管张力。尽管这种调节系统在所有脊椎动物中都存在，但这些内皮源性物质的释放存在很大的异质性，在不同器官之间、大小血管之间以及不同物种之间均有差异。因此，在某些血管床或动物身上的观察结果不一定适用于人体眼循环。本研究旨在调查人体眼动脉中的内皮介质。结果表明，在人体眼动脉中，一氧化氮在基础条件下释放，其生成可被缓激肽、乙酰胆碱，尤其是组胺显著刺激，这些物质可引起血管深度舒张。相比之下，内皮素-1引起强烈收缩，这种收缩不受钙拮抗剂硝苯地平的影响。然而，当血管再次暴露于该肽时，明显出现快速耐受性。这些发现表明，在人体眼动脉中，内皮源性一氧化氮和内皮素是血管张力的强效调节剂，提示它们在调节眼部局部血流中起重要作用。因此，内皮功能障碍可能是与眼部血流改变相关疾病状态（如糖尿病、高血压和某些类型的低眼压性青光眼）的一种新的发病机制。
