[Nitrergic reactivity in endothelial cells of human uveal blood vessels]

We investigated the presence of Nicotinamid-adenin-dinucleotid-phosphat (NADPH)-diaphorase activity in endothelial cells of the human uveal vessels, using a histochemical procedure which presumably localizes the reaction product nitric oxide.

11 donor eyes destined for corneal transplantation (male: 6; female: 5; age: 56 +/- 8 years) were used within 14 +/- 7 h postmorten. After removal of the cornea and retinal pigment epithelium, flat mounts of the choroid were made. Serial sections, 12-16 microns in thickness were cut from the ciliary body and iris using a cryomicrotome. Sections mounted on chromalaun-gelatine-coated glass slides, treated according the standard NADPH-diaphorase reaction and finally mounted in Kayser's glycerol-gelatine prior to examination in the light microscope.

Human choroidal vascular endothelial cells revealed positive NADPH-diaphorase activity, which was detected by the presence of punctate blue staining in the cytoplasm. No significant difference in distribution pattern or area density was seen amongst small and large vessels in either choroid, ciliary body or iris. Ganglion cells in the choroid and ciliary body also exhibited NADPH-diaphorase reactivity.

The presence of NADPH-diaphorase reactivity in vascular endothelial and ganglion cells of the human choroid suggests a possible nitrergic relaxation mechanism in human uveal vasculature.