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- Title
Role of protein kinase C in regulation of Na<sup>+</sup>- and K<sup>+</sup>-dependent ATPase activity and pump function in corneal endothelial cells.
- Authors
Masakazu Yamada; Hiroshi Mochizuki; Teruo Nishida
- Abstract
Abstract Purpose Na+- and K+-dependent ATPase (Na,K-ATPase) plays an important role in the pump function of the corneal endothelium. We investigated the possible role of protein kinase C (PKC) in regulation of Na,K-ATPase activity and pump function in corneal endothelial cells. Methods Confluent monolayers of mouse corneal endothelial cells were exposed to phorbol 12,13-dibutyrate (PDBu) to induce activation of PKC. ATPase activity of the cells was evaluated by using ammonium molybdate in spectrophotometric measurement of phosphate released from ATP, with Na,K-ATPase activity being defined as the portion of total ATPase activity sensitive to ouabain. Pump function of the cells was measured with a Ussing chamber, with the pump function attributable to Na,K-ATPase activity being defined as the portion of the total short-circuit current sensitive to ouabain. Results PDBu (10−7 M) increased the Na,K-ATPase activity and pump function of the cultured cells. These effects of PDBu were potentiated by the cyclooxygenase inhibitor indomethacin and the cytochrome P450 inhibitor resorufin and were blocked by okadaic acid, an inhibitor of protein phosphatases 1 and 2A. Conclusions Our results suggest that PKC bidirectionally regulates Na,K-ATPase activity in mouse corneal endothelial cells: it inhibits Na,K-ATPase activity in a cyclooxygenase- and cytochrome P450-dependent manner, whereas it stimulates such activity by activating protein phosphatases 1 or 2A.
- Subjects
PROTEIN kinase C; SODIUM/POTASSIUM ATPase; ENZYME regulation; CORNEA; ENDOTHELIUM; EPITHELIAL cells
- Publication
Japanese Journal of Ophthalmology, 2009, Vol 53, Issue 3, p235
- ISSN
0021-5155
- Publication type
Article