Characterization of soluble guanylyl cyclase in transformed human non-pigmented epithelial cells

Topical application of nitro vasodilators, such as sodium nitroprusside, reduces intraocular pressure. In brain and blood vessels, nitro vasodilators activate soluble guanylyl cyclases, producing cGMP. The location and molecular identity of ocular guanylyl cyclases are unknown. We studied transformed human non-pigmented ciliary epithelial cells, whose parental cells are responsible for the production of aqueous humor. Sodium nitroprusside increased cGMP 40 to 60 fold in a time and concentration dependent manner (EC₅₀ 40 to 100 μM). Methylene blue inhibited this effect (IC₅₀ 0.6 μM in th presence of 100 μM sodium nitroprusside). We also detected mRNA for the α1 and β1, but not the β2, subunit isoforms of soluble guanylyl cyclase in these cells by Northern blotting. We conclude that transformed non-pigmented epithelial cells contain an active heterodimeric soluble guanylyl cyclase composed of at least α1 and β1 subunits.