Alteration of active Na-K transport on protein kinase C activation in cultured ciliary epithelium.
OBJECTIVE
Experiments were conducted to test whether protein kinase C activation causes changes in active sodium-potassium transport in an established SV-40 transformed line (ODM2) of cultured human nonpigmented ciliary epithelial cells.


METHODS
Rubidium-86 (86Rb) uptake was measured and the data used to determine the rate of potassium entry into the cells.


RESULTS
Protein kinase C activator, phorbol dibutyrate (PDBu), caused a stimulation of ouabain-sensitive 86Rb uptake. Inhibition of protein kinase C by 1-(5-isoquinolinylsulfonyl) 2-methylpiperazine (H-7), or down-regulation of protein kinase C activation by prolonged exposure of PDBu, decreased the PDBu response. These results suggest that protein kinase C plays a role in Na-K pump activation. The Na/H+ exchanger inhibitor, amiloride, also reduced the stimulation of the ouabain-sensitive 86Rb uptake by PDBu. 86Rb efflux was not altered by protein kinase C activation. At the same time that PDBu increased the ouabain-sensitive 86Rb uptake, it also decreased the ouabain-insensitive 86Rb uptake. The ouabain-insensitive 86Rb uptake component could be inhibited by bumetanide, suggesting that protein kinase C activation decreases the activity of a Na/K/2Cl cotransporter.


CONCLUSIONS
These findings suggest that activation of protein kinase C may stimulate Na,K-ATPase activity mainly by a mechanism involving increased Na+ influx mediated by the Na+/H+ exchanger.
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Department of Ophthalmology and Visual Sciences, Kentucky Lions Eye Research Institute, University of Louisville School of Medicine 40292.
Delamere
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D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000584:Amiloride / Q000494:pharmacology; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000502:physiology; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D002924:Ciliary Body / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012414:Rubidium Radioisotopes / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism / Q000502:physiology
D002352:Carrier Proteins; D007546:Isoquinolines; D010879:Piperazines; D012414:Rubidium Radioisotopes; D017923:Sodium-Hydrogen Exchangers; D015240:Phorbol 12,13-Dibutyrate; D010042:Ouabain; D000584:Amiloride; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D012964:Sodium; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium