Ocular responses to leukotriene C 4 and D 4 in the cat

Abstract

The effects of leukotriene C 4 (LTC 4) and D 4 (LTD 4) on the iridial smooth muscles, intraocular pressure, blood-aqueous barrier and regional blood flow in the eye have been studied in cats. The test compounds were injected into the anterior chamber. Both LTC 4 and LTD 4 caused a dose-dependent constriction of the pupil, the agents being about equipotent. The effect on the iridial sphincter muscle was not dependent on nerve conduction, cyclo_oxygenase products or muscarinic receptors. Maximal constriction was achieved with 0.1–1 μg of the test compounds. The smallest dose to induce a decrease in pupil diameter was 0.01 μg. After intracameral injection of 4 μg the miotic response was markedly delayed. This indicates that in high concentrations LTC 4 and LTD 4 probably also stimulate the iridial dilator muscle. The blood flow in the anterior uvea decreased after intracameral injection of 4 μg LTC 4/LTD 4. Small doses had no clear effect. There was no effect on the blood-aqueous barrier as judged from the aqueous humor protein concentration. The intraocular pressure decreased slightly after injection of the test compounds.