Studies on leukotriene D4 as an eosinophil chemoattractant.

The effects of LTD4 on eosinophil motility were studied in order to indicate its potential role as an eosinophil chemoattractant. The guinea pig was selected as a suitably sensitive species for in vivo studies. Eosinophil infiltration was quantified by digital image analysis of 6 microns paraffin ocular and cutaneous tissue sections stained by Luna's method. LTD4, applied topically to the ocular surface, caused pronounced eosinophil infiltration into the conjunctival epithelium and was more potent and efficacious than a variety of other putative mediators of allergy. Pretreatment with the LT-antagonist SK&F 104353 (i.v. 1 mg/kg) abolished LTD4-induced eosinophil infiltration into the conjunctiva. Eosinophil infiltration did not occur in other ocular anterior segments structures such as the cornea, iris and ciliary body after either topical application or intracameral injection. LTD4 did not cause eosinophil emigration into skin following intradermal injection, despite causing an increase in cutaneous microvascular permeability at identical doses. These studies indicate that LTD4 may cause eosinophil emigration in vivo according to tissue-dependent regulation.