EFFECT OF LIGHT AND DARKNESS ON NUCLEIC ACIDS AND PROTEIN METABOLISM OF PINEAL GLAND

Exposure of female rats to continuous light from the day of weaning - 21st day of age - for ten, twenty and thirty days caused a significant inhibition in their pineal RNA and protein synthesis, amounting to 20 per cent compared with control animals kept in conditions of alternating light and darkness. The main inhibition occurred within the first ten days of exposure, coinciding with the period of most active physiological production of nucleotides and proteins. No change was found in the pineal DNA levels of the rats exposed to continuous light, indicating that the reduced RNA and protein results from a decreased cellular metabolism unrelated to physiological cell multiplication. This would imply an inhibition of parenchymal hypertrophy of the pineal under conditions of continuous light. The three parameters tested were the same in rats exposed to continuous darkness and animals kept under an alternating diurnal light-dark cycle. © 1969.