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F. P. Diecke, L. Ma, P. Iserovich, J. Fischbarg; The Role of Protein Kinase C (pkc) in the Regulation of Fluid Transport Across Rabbit Corneal Endothelium. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3998.
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The regulation of fluid transport across the corneal endothelium by extra- and intracellular messengers is poorly understood. We have examined the effects of modulation of PKC with activators and inhibitors on corneal fluid transport.
Corneas were obtained from New Zealand albino rabbits (~2 kg) using procedures in accordance with NIH guidelines. Transendothelial fluid movement was determined by measuring the changes in corneal thickness with the Dikstein-Maurice method. Corneal thickness was determined with a computer-controlled specular microscope, which automatically sensed and recorded it at 5-minute intervals. Fluid transport was calculated from the rates of corneal thickness change as reported previously.
Inhibition of PKC activity with calphostin C, an inhibitor of conventional and novel PKC isoforms, resulted in a dose-dependent increase in fluid movement and a reduction of corneal thickness. The effect of PKC activators was found to be more complex. Phorbol-12, 13- dibutyrate (PDBu) and Phorbol-12-myristate-13-acetate (PMA) produce an initial increase followed by a reduction in fluid transport. We have further attempted to identify the membrane component affected by PKC modulation. Corneal swelling in bicarbonate-free solutions was temporarily arrested by exposure to 1 µM calphostin C. However, if corneal swelling was induced by inhibition of anion channels using a cocktail of 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and niflumic acid (NA) both 100 µM, then exposure to Calphostin C did not affect the rate of swelling.
Activation of PKC may result in an initial activation of fluid transport followed by inhibition of it. Such activation and/or inhibition may be due to effects on anion channels.
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