Conjunctival leukocyte infiltration evoked by leukotrienes: differing responses among rodent species

Application of leukotrienes (LT) B4 or D4 to the guinea-pig eye evokes conjunctival eosinophil infiltration, providing an in vivo model of tissue eosinophilia. To determine if other rodent species would respond similarly, LTB4 or LTD4 were applied to the right eye of male mice and rats (three per group) at doses of 250, 1000 or 5000 ng/eye (mice) and 1000 or 5000 ng/eye (rats). Left eyes received the same volume (mice, 5 microliters; rats, 20 microliters) of vehicle (isotonic saline). Conjunctivae were evaluated histologically 6 h after application. In mice, 1000 or 5000 ng/eye LTB4 resulted in mild conjunctival neutrophilia, but no leukocyte response to LTD4 was observed. In rats, no leukocyte responses, either to LTB4 or to LTD4, were observed. The results illustrate interspecies differences in leukocyte responsiveness to LT and indicate specifically that, unlike the guinea pig, neither mouse nor rat responds to LT with conjunctival eosinophilia.