Effect of brief constant darkness and illumination on mitochondrial respiratory control of the pineal gland, Harderian gland, spleen and thymus of adult rat [Efeitos da escuridão e da luminosidade breve e constante no controle da respiração mitocondrial das glándulas pineal, Harderiana, baño e timo]

Abstract

Background and objectives: Constant environmental conditions can lead to changes in the synthesis of melatonin. In vitro studies have shown that this hormone modulates the efficiency of mitochondrial respiration. Therefore, this work examined whether the efficiency of mitochondrial respiration changes in rats that have been subjected to constant illumination or darkness for a short period. Methods: Rats were randomly distributed in three groups: Control, Constant Illumination (72 hours) and Constant Darkness (72 hours). Upon completion of treatment, rats were sacrificed and mitochondria from the pineal gland, Harderian gland, thymus and spleen were isolated. Subsequently, mitochondrial respiratory control was quantified from the removed tissues in the three experimental groups. Results: Our findings show that brief treatments of continued illumination or continued darkness had no significant effect on mitochondrial respiratory control in spleen, thymus or Harderian glands. In contrast, we observed a slight increase in mitochondrial respiratory control in the pineal gland of animals exposed to constant illumination. Conclusions: Our results suggest that brief treatment with continuous light or darkness does not have a significant effect on the efficiency of mitochondrial activity in spleen, thymus or Harderian gland. This is probably due to the endogenous circadian rhythms that tightly regulate mitochondrial enzymatic activity in these tissues