Complex Granules

With the increasing of age, melanin, lipofuscin, and lysosomes can join together to form complex structures (melanolipofuscin and melanolysosomes) inside the RPE. These granules have a regional distribution similar to that of lipofuscin; i.e., the highest concentration is in the macula, and it decreases in the periphery and in the fovea. Concerning the percentage of the cellular volume occupied by complex granules, this varies from 3.3% in the first decade of life and reaches to 8 to 10% in the sixth decade. The association of lysosomes with pigment granules (for example, melanosomes, lipofuscin granules, and complex pigments) explains their age-dependant variation observed in the lysosomal enzyme levels and the activity of the RPE cells. The increase in pigment granules with age causes an increase in lysosomes and in the activity of various enzymes such as acid phosphatase and Cathepsin D, in order to maintain the normal degradation cycle, which follows the ingestion of the acromeres of the photoreceptors by the RPE cells (Boulton et al., 1998).

Was this article helpful?

0 0
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...

Get My Free Ebook

Post a comment