Cellular and vascular responses in acute experimental ocular inflammation.

ABSTRACT

PURPOSE: To measure simultaneously blood volume, altered vascular permeability, and leukocyte extravasation in ocular inflammation in rabbits at various times and in different anatomic locations after intravitreal endotoxin (lipopolysaccharide [LPS]). METHODS: Nuclides of different emission and decay were used for labeling and then injected intravenously. Ocular blood volumes were measured with technetium 99m, altered vascular permeability with I-125 albumin, and polymorphonuclear leukocyte or mononuclear cell extravasation after labeling with Indium 111. Eyes were divided into anterior eye section, iris-ciliary body, aqueous, and vitreous and posterior eye sections, and measurements were made at 3, 6, 9, 18, and 24 hours after intravitreal LPS injection. Blood volume measurements made it possible to estimate the amount of extravascular protein and the number of extravascular leukocytes. RESULTS: Blood volumes were consistently elevated at all times, usually by approximately 50% and predominantly in the anterior segment. Altered vascular permeability was present at 3 hours, increased at 6 hours, decreased at 9 hours, and was elevated at 18 to 24 hours, predominantly in the anterior eye. Leukocytes in iris-ciliary body appeared in small numbers at 6 hours, increased at 9 hours, and continued to extravasate at 18 and 24 hours. Mononuclear cells were as numerous as polymorphonuclear leukocytes at each time measured. CONCLUSIONS: The quantitation of multiple parameters of ocular inflammation in this experimental model has been helpful in defining when and in what tissue changes occur. Leukocytes are primarily within tissues, particularly in the iris-ciliary body region. Mononuclear leukocytes are a prominent feature at all times and add further support to the concept that the mononuclear phagocyte plays a pivotal role in reactions to LPS.