PMID: 9660493Jul 11, 1998Paper

Dopamine D1 stimulation of Na+,K+,Cl- cotransport in human NPE cells: effects of multiple hormones

Investigative Ophthalmology & Visual Science
K RieseR B Crook

Abstract

To determine the effects of dopamine on Na+,K+,Cl- cotransport in human ciliary nonpigmented epithelial (NPE) cells. The authors used 86Rb+ as a marker for K+ to study ouabain-insensitive, bumetanide-sensitive 86Rb+ uptake in cultured fetal human NPE monolayers. Na+,K+,Cl- cotransport was stimulated 1.63-fold by 10 microM dopamine. Stimulation was dose dependent, with a maximum stimulation occurring at 10 microM dopamine and an EC50 of 0.5 microM. NaK-ATPase (measured as ouabain-sensitive, bumetanide-insensitive 86Rb+ uptake) and bumetanide-insensitive, ouabain-insensitive 86Rb+ uptake were not affected by dopamine. The D1-receptor-specific antagonist, SCH23390, inhibited stimulation by 10 microM dopamine more than 90% at 1 microM, with an IC50 of 4 nM, whereas the D2-receptor-specific antagonist, sulpiride, was over 250 times less effective. Similarly, a D1 agonist, SKF81297, was more potent than the D2 agonist bromocriptine in stimulation of Na+,K+,Cl- cotransport. The beta-adrenergic antagonists timolol and propranolol did not significantly inhibit stimulation of Na+,K+,Cl- cotransport by dopamine. Conversely, SCH23390, showed minimal inhibition of isoproterenol stimulation of Na+,K+,Cl- cotransport. Stimulation by maximally...Continue Reading

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