Atrial natriuretic peptide stimulates Cl-transport in retinal pigment epithelial cells

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Abstract
To study the regulatory role of atrial natriuretic peptide (ANP) on the Cl- transport activity of retinal pigment epithelial (RPE) cells, RPE cells from rabbits were cultured and exposed to ANP and other reagents under perfusion. The changes in intracellular Cl- concentration ([CI-]i) were continuously recorded using a Cl--sensitive fluorescent dye. The cGMP content was estimated by radioimmunoassay. ANP increased the cGMP content and the [Cl-], in RPE cells. A guanylate cyclase activator, nitric oxide, and a cell permeable cGMP precursor, 8-Br-cGMP, also increased the level of cGMP and the [Cl-]i. A guanylate cyclase inhibitor, LY83583, an inhibitor of cGMP-dependent protein kinase, KT5823, and an inhibitor of Na+/K+/2Cl- cotransporter, bumetanide, diminished or abolished the ANP-induced increase in [Cl-];. ANP facilitates Cl- accumulation in RPE cells, which is mediated by guanylate cyclase, cGMP-dependent protein kinase, and the Na+/K+/2Cl- cotransporter.