Pineal and retinal lysosomal enzyme rhythms

Pineal glands and the neurosensory portion of the retinae of adult male rats adapted to a 24-h cycle with lights on from 06.00 to 20.00 h were collected at 9 timepoints during the cycle. Significant rhythms in both pineal and retinal hexosaminidase, β-glucuronidae, acid phosphatase and β-glucosidase were observed. For each enzyme, pineals had greater overall activity per unit amount of protein than did retinae. All 4 significantly rhythmic pineal enzymes peaked within 30 min of each other (18.30-19.00 h) whereas the retinal enzymes peaked some 6h earlier, between 11.30 and 13.45 h. To our knowledge, this is the first report demonstrating 24-h rhythms in lysosomal enzymes in the pineal gland and retina. Since the acrophases (peak time) of these enzymes within each tissue are tightly synchronized yet different between tissues, lysosomes may play unique roles in the physiology of different structures in the photoneuroendocrine system with respect to time in the light-dark cycle.