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 identified and localised using a potent TxA(2) specific agonist, (125)-iodinated 5-heptenoic acid 7-[3-[3-hydroxy-4-[4-(iodo-I-125) phenoxy]-1-butenyl]-7-oxabicyclo[2.2.1]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 within ocular tissues, including the corneal epithelium, the ciliary processes, retina, and posterior ciliary arteries, In addition, we have used 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 order to obtain enhanced cellular resolution and more detailed information about the localisation of the receptors and their corresponding mRNAs, 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 cells of the posterior ciliary arteries. These results may be helpful for understanding the pathophysiological effects of TxA(2) in the human eye.