EFFECT OF MELATONIN ON BIOPHYSICAL PROPERTIES OF RETINAL RHODOPSIN

Abstract

Melatonin was recognized as an important neuroendocrine hormone that affects a variety of peripheral endocrine organs. Recently melatonin is a broad-spectrum antioxidant for both animals and plants. It prevents oxidative damage at the level of cells, tissues, organs and organisms. In addition it preserves mitochondrial function and protect both membrane lipids and nuclear DNA from oxidative damage. In the eye melatonin is detectable in the retina, iris, ciliary body and aqueous humor. In addition, retinal melatonin synthesis fluctuates in a circadian fashion and functions as rod photoreceptor disk shedding and dark-adaptive retinomotor movements. It has been known that melatonin has an anticataract function and reduce lipid peroxidation.

So, in the present study the effect of different doses of melatonin on the retinal rhodopsin was studied after different periods. The animals (Newzealand and white rabbits) were grouped into five sets (I, II, III, IV and V). Animals of set I was used as a control. Sets (II, III, IV and V) were injected daily with melatonin by doses of (10, 100, 500 and 1000JJ,g) respectively for the periods of 24 hours, one month, three months and five months. The rabbits were injected with melatonin daily in the early morning. After the studied periods, the rabbits decapitated, the eyes were enucleated immediately. The retinas were separated and rhodopsin was extracted, then the following measurements were carried out on it:

a) Measurement of the UV and visible absorption spectrum.