Localization of EP1 and FP receptors in human ocular tissues by in situ hybridization

PURPOSE. To examine the expression and localization of EP1 and FP receptor mRNAs in normal human ocular tissues by in situ hybridization. METHODS. Digoxigenin-labeled human EP1 and FP receptor antisense and sense riboprobes were used for in situ hybridization on paraffin sections of norm al human eye tissue. RESULTS. In situ hybridization revealed the presence of high levels of both EP1 and FP receptor mRNA transcripts in the blood vessels of iris, ciliary body, and choroid. Both the endothelial and smooth muscle cells of blood v essels demonstrated intense hybridization signals corresponding to EP1 rece ptor mRNA transcript. EP1 receptor hybridization signals were present in al l the muscle fibers of the ciliary body. In the retina, hybridization signa ls for EP1 receptors were observed in photoreceptors and both nuclear layer s and in ganglion cells. The hybridization signals corresponding to FP rece ptor transcript were similar to those of EP1 receptors in the iris tissues, in the ciliary muscle, FP receptor mRNA transcript was predominantly prese nt in the circular muscle and in the collagenous connective tissues; no hyb ridization signal for this receptor was observed in the retina. CONCLUSIONS. The wide distribution of EP1 and FP receptor mRNAs in human oc ular tissues appears to be localized in the functional sites of the respect ive receptor agonists. Selective localization of FP receptor mRNA in the ci rcular muscles and collagenous connective tissues of the ciliary body sugge sts their involvement in the increased uveoscleral outflow of aqueous humor by PGF(2 alpha).