Comparison of the Ocular Effects of Circulating Endotoxin and Immune Complexes: Role of Vasoactive Amines¹

Both bacterial endotoxin and soluble immune complexes (BGG-anti BGG) injected i.v. in rabbits produce an alteration in ocular vascular permeability confined primarily to the vessels of the iridial portion of the ciliary processes. These effects have been measured by the ocular accumulation of ¹²⁵I-albumin relative to cardiac plasma. Ten micrograms per kilogram of Escherichia coli bacterial endotoxin (055:B5) produce a consistent alteration in ocular vascular permeability over a 90-min period after injection. Fifty to 100 µg/kg of endotoxin result in a prolonged effect that is maximum 4 hr after injection.

Large quantities of immune complexes (BGG-antiBGG) prepared in 20 to 25 times antigen excess produce an anaphylaxis and approximately a 70% reduction in platelets and CH₅₀. The alteration in ocular vascular permeability is half as great as that produced by 10 µg/kg of endotoxin over the 90-min period after their injection. A combined treatment with antihistamine, pyrilamine maleate, and antiserotonin, methysergide maleate, results in a significant reduction in ocular ¹²⁵I-albumin in normal animals, virtually prevents the ocular effect of immune complexes, and reduces the average effect of endotoxin by 30%. Increasing the quantities of injected antihistamine and antiserotonin does not have a further effect on the response to 10 µg of endotoxin.