Localisation of thromboxane A2 receptors and the corresponding mRNAs in human eye tissue.

Thromboxane A2 (TxA2) receptors in human eye sections were identified and localised using a potent TxA2 specific agonist, 125-iodinated 5-heptenoic acid 7-[3-[3-hydroxy-4-[4-(iodo-125I) phenoxy]-1-butenyl]-7- oxabicyclo[2.2.1]hept-2-yl]-,[1S-[1a,2a,(Z),3B(1E,3S*),4a]]-C23 H29 IO5 (125I-BOP) in a binding assay. TxA2 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 TxA2 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 TxA2 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 TxA2 in the human eye.