CELLULAR AND VASCULAR-RESPONSES IN ACUTE EXPERIMENTAL OCULAR INFLAMMATION

Purpose. To measure simultaneously blood volume, altered vascular perm eability, and leukocyte extravasation in ocular inflammation in rabbit s at various times and in different anatomic locations after intravitr eal endotoxin (lipopolysaccharide [LPS]). Methods. Nuclides of differe nt emission and decay were used for labeling and then injected intrave nously. Ocular blood volumes were measured with technetium 99m, altere d vascular permeability with 1-125 albumin, and polymorphonuclear leuk ocyte or mononuclear cell extravasation after labeling with Indium 111 . Eyes were divided into anterior eye section, iris-ciliary body, aque ous, and vitreous and posterior eye sections, and measurements were ma de at 3, 6, 9, 18, and 24 hours after intravitreal LPS injection. Bloo d volume measurements made it possible to estimate the amount of extra vascular protein and the number of extravascular leukocytes. Results. Blood volumes were consistently elevated at all times, usually by appr oximately 50% and predominantly in the anterior segment. Altered vascu lar permeability was present at 3 hours, increased at 6 hours, decreas ed at 9 hours, and was elevated at 18 to 24 hours, predominantly in th e anterior eye. Leukocytes in iris-ciliary body appeared in small numb ers at 6 hours, increased at 9 hours, and continued to extravasate at 18 and 24 hours. Mononuclear cells were as numerous as polymorphonucle ar 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 tissues changes occur. L eukocytes are primarily within tissues, particularly in the iris-cilia ry body region. Mononuclear leukocytes are a prominent feature at all times and add further support to the concept that the mononuclear phag ocyte plays a pivotal role in reactions to LPS.