Functional Role Of

The RPE plays a fundamental role in the transport and storage of the retinoids, essential for maintaining the visual cycle. Another function of the RPE is to eliminate components of the acromeres of the photoreceptors through phagocytosis activity mediated by cathepsin D and by the integrins that act as membrane receptors that mediate the phagocytosis. The phagosomes are linked to lysosomes to form phagolysosomes, where they are digested by the intracellular digestive enzymes located at the basal surface of the cell. The final metabolism products are expelled into the choroidal circulation by exocytosis through the Bruch's membrane. If they are not completely digested, they accumulate inside the cells as granules of lipofuscin. These granules increase with age (Iwasaki and Inomata, 1988), especially in the macular area. The constant exposure of the RPE to light, at elevated concentrations of oxygen, together with the high metabolic activity of these cells, creates an environment favorable, especially in the macular area, to the formation of toxic reactive oxygen radicals. In defense against oxidative stress, the RPE cells contain antiox-idants such as superoxide dismutase, catalases, reduced glutathione, melanin, and carotenoids. In reality, the quantity of these reduces with age, as the antioxidant defenses decrease.

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Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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