LOCALIZATION OF THROMBOXANE A(2) RECEPTORS AND THE CORRESPONDING MESSENGER-RNAS IN HUMAN EYE TISSUE

Thromboxane A(2) (TxA(2)) receptors in human eye sections were identif ied and localised using a potent TxA(2) specific agonist, (125)-iodina ted 5-heptenoic acid 7-[3-[3-hydroxy-4-[4-(iodo-I-125) .1]hept-2-yl]-, [1S-[1a,2a,(Z),3B(1E,3S),4a]]-C-23 H-29 IO5 (I-125-BOP) in a binding assay. TxA(2) receptors were concentrated in several specific loci wit hin ocular tissues, including the corneal epithelium, the ciliary proc esses, retina, and posterior ciliary arteries, In addition, we have us ed the method of in situ hybridisation to observe the distribution of TxA(2) receptor mRNA. The distributions of both receptor binding sites and receptor mRNAs showed a close correlation. These studies employed film autoradiography which does not permit cellular resolution. In or der to obtain enhanced cellular resolution and more detailed informati on about the localisation of the receptors and their corresponding mRN As, emulsion autoradiography was used after ligand binding and in situ hybridisation. This approach showed further that TxA(2) receptors are mainly concentrated on non-pigmented epithelial cells of the ciliary processes, on photoreceptors within the retina, and on endothelial cel ls of the posterior ciliary arteries. These results may be helpful for understanding the pathophysiological effects of TxA(2) in the human e ye.