Prolonged Light Deprivation Modulates the Age-Related Changes in α-Tocopherol Level in Rats

The light-dark cycle is one of the main environmental factors affecting the rhythm of biological processes in the body. A change or absence of this cyclicity leads to disruption of circadian rhythms and negatively affects the functioning of all body systems. The aim of the study was to investigate the effect of constant darkness, which began from the prenatal period (DD/DD) or from the moment of birth (LD/DD) and continued throughout life, on the content of alpha-tocopherol in Wistar rats in late ontogenesis (3, 6, 12, 18 and 24 months). Control animals were kept under standard light conditions (LD). The level of alpha-tocopherol was determined by HPLC. The modulating effect of long-term light deprivation was found in the liver, skeletal muscle and lungs, most of the changes were observed in 12-month-old rats. Thus, in the liver the level of vitamin decreased in both experimental groups, which is probably due to the regulatory role of the organ in maintaining vitamin E homeostasis in the body. In the skeletal muscle of rats from the DD/DD group, a significant increase in the content of alpha-tocopherol was found. This may show the accumulation of lipids in myocytes as a result of disorder of homeostasis of the main energy substrates of skeletal muscles. In 24-month-old rats of this group, the vitamin level in the tissue was significantly lower than in the control, which may indicate a decrease in the antioxidant protection of the skeletal muscle due to age-related changes. In rats, exposed to constant darkness after birth, there were differences in the direction of changes in the lungs alpha-tocopherol level compared with the control group at the age of 6 and 12 months. In aging and old animals, the effect of light deprivation was probably smoothed out by age-related disturbances of the circadian system thus in most of the studied tissues the vitamin content did not differ in rats of the control and both experimental groups. The results can be useful in assessing the physiological state of people working or living under poor lighting conditions.