DISTRIBUTION AND CHARACTERIZATION OF RAT CHOROIDAL MAST-CELLS

Despite the implication that choroidal mast cells are involved in the onset of experimental autoimmune uveoretinitis (EAU), a widely used an imal model of uveoretinitis, little is known of these cells. In the pr esent study the distribution, total number, regional density, and phen otype of choroidal mast cells were examined in Lewis, Wistar Furth, PV G/c, and brown Norway rats. Choroidal mast cells were predominantly as sociated with arteries and arterioles of more than 30 mu m diameter wh ich lie in the outer (sclerad) choroid. The density of mast cells was greatest in the posterior choroid with density diminishing anteriorly. The choroid of male Lewis rats contained significantly greater number of mast cells than that of females (p<0.01). Histochemical (Alcian bl ue/safranin) and immunohistochemical (anti-rat mast cell protease I an d II monoclonal antibodies) studies revealed choroidal mast cells were of the connective tissue type. However, granule proteinase content ap peared less than that of well characterised connective tissue mast cel l populations such as those in mesentery and skin. Lewis rats exhibite d the highest density of choroidal mast cells (23.6 (SD 1.2)/mm(2)), W istar Furth approximately half that of Lewis (13.5 (0.7)/mm(2)) while PVG/c and brown Norway rats had very low densities (3.06 (0.3); 1.95 ( 0.2)/mm(2) respectively). These studies provide valuable choroidal mas t cell data for rats which may have implications for our understanding of experimental models of intraocular inflammation and clinical uveit is.