The study was designed to investigate the effect of exposure to long-term constant
darkness, starting from the prenatal period or from birth, on the retinol (vitamin A) content in
tissues of rats. Females were kept in standard light (LD) or in constant darkness (DD) during
pregnancy. The LD females and their offspring after birth were divided into two groups,
one of which was left in the same lighting conditions (LD, control), and the other group was
switched to the darkness regime (LD/DD). The DD females and their offspring (DD/DD) were
kept in the dark. Adults and the young were separated after the suckling period. The retinol
content in offspring’s tissues (liver, kidneys, heart and skeletal muscle) was determined at
the age of 2 weeks, 1, 2, 3, 6, 12, 18 and 24 months by HPLC. Constant darkness had a
modulating effect on the age-related dynamics of retinol content in the tissues. The level
of the vitamin was higher compared to the control animals in the liver of 2-week-old LD/DD
rats and in the kidneys of 1-month-old rats of both experimental groups. The retinol content
in the heart of 2-month-old DD/DD rats, on the contrary, was significantly lower than in the
control. The retinol level in the liver of 12-month-old LD/DD rats was higher compared to
the control animals. The effect of constant darkness on retinol level in tissues depended on
the ontogenesis stage at which the experimental exposure began, the tissue type, and the
animal’s age. The retinol content in the tissues of rats kept in constant darkness indicates
metabolic changes that were more pronounced in young animals.