Ismail M, al-Bekairi A M, el-Bedaiwy A M, Abd-el Salam M A
Department of Pharmacology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia.
J Toxicol Clin Toxicol. 1993;31(1):31-41. doi: 10.3109/15563659309000372.
Venom from the ringhals cobra (H. haemachatus) caused extensive chemosis, prolonged corneal edema and marked miosis when applied locally to the eyes of two strains of rabbits: Buskat (albino) and Chinchilla (pigmented). In the pigmented rabbits, the corneal edema progressed to complete corneal opacification with corneal and conjunctival neovascularization that remained unchanged until the end of the experiment (70 d). In the albino rabbits the corneal cloudiness and conjunctivitis cleared within three weeks of venom instillation. Treatment with heparin and tetracycline markedly improved the corneal opacification syndrome, while treatment with specific antivenom resulted only in partial improvement. It is postulated that the venom owes its ocular effects to its cardiotoxin, the only venom fraction capable of inducing the corneal opacification syndrome. The protective effect of heparin is probably through its electrostatic binding to the cardiotoxin in the venom. Tetracycline could form ionic bonding at several sites in the strongly basic cardiotoxin. The corneal opacification syndrome was associated with the ability of the snakes to spit since venoms from the other non-spitting cobras were devoid of this activity.
喷毒眼镜蛇（黑颈射毒眼镜蛇）的毒液局部滴入两种品系兔子（布氏兔（白化）和青紫蓝兔（有色））眼内时，可引起广泛的球结膜水肿、角膜水肿持续时间延长以及显著的瞳孔缩小。在有色兔子中，角膜水肿发展为完全性角膜混浊，并伴有角膜和结膜新生血管形成，直至实验结束（70天）时仍无变化。在白化兔子中，毒液滴入三周内角膜混浊和结膜炎消退。肝素和四环素治疗可显著改善角膜混浊综合征，而特异性抗蛇毒血清治疗仅能部分改善。据推测，该毒液的眼部效应归因于其心脏毒素，这是唯一能够诱发角膜混浊综合征的毒液成分。肝素的保护作用可能是通过其与毒液中心脏毒素的静电结合。四环素可在强碱性心脏毒素的多个位点形成离子键。角膜混浊综合征与蛇的喷毒能力有关，因为其他非喷毒眼镜蛇的毒液没有这种活性。
