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P. de la Villa, L. Ramirez, J. Vicente; Expression and Activation of Protein Kinase C in Rod Bipolar Cells Depends of the Circadian Rhythm. Invest. Ophthalmol. Vis. Sci. 2008;49(13):179.
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To elucidate the physiological mechanisms that determine the activation or protein kinase C alpha (αPKC) in rod bipolar cells (RBC) of the mouse retina and its functional role in the light or dark phases of the circadian rhythm.
Control C57BL6j and dystrophic rd10 mice were used along the experiments. Immunoreactivity against the αPKC was performed on transverse sections of control and dystrophic mouse retinas at different periods of their circadian rhythm. In another series of experiments, activation of αPKC was tested by Western blotting. Mouse eyes were enucleated and cytosolic and membrane contents of αPKC were analyzed from retinas isolated at different periods of the circadian rhythm. Proteins from the cytosolic and membrane compartments were isolated and transferred to nitrocellulose membranes and analyzed by using an anti-αPKC monoclonal antibody.
Immunoreactivity to αPKC at different periods of the mouse circadian rhythm shows that the intensity of the immunoreactions is higher in the axon terminal of RBC than in the soma at the end of the light hours. On the contrary, immunoreactivity to αPKC is homogeneously distributed in the soma and axon terminal of RBC at the end of the dark hours. Experiments performed in rd10 dystrophic animals do not show any difference in the degree of immunoreactivity to αPKC between soma or axon terminal of RBC from dark or light phases of the circadian rhythm. Analysis of the αPKC translocation at different times of the circadian rhythm indicates that αPKC is continuously translocated during the light hours whereas it is mainly located in the cytosolic compartment at the end of the dark hours.
The present results show that retinal adaptation during the day phase of the circadian rhythm involves the activation of αPKC in the mouse and its transport to the axon terminal of RBC. Our findings also suggest that αPKC plays its functional role in RBC, probably modulating the day/night adaptive mechanisms of the retina.
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