Pineal lysosomal enzyme circadian rhythms in male hamsters exposed to natural decreasing photoperiod and temperature conditions

Circadian rhythms in acid phosphatase (ACP), hexosaminidase (HEX) and β-glucuronidase (RON) activity were studied in the pineal glands of adult male Syrian hamsters exposed to control (20 ± 2°C and 14:10 LD) conditions or to naturally decreasing autumn photoperiod and temperature conditions (outside) for 8 weeks. Testes and testosterone levels (p < 0.001 in both instances) were severely depressed in animals exposed to natural environmental conditions illustrating that the treatment period was of sufficient length to produce pineal-mediated gonadal atrophy. Significant rhythms were found in all enzymes in the pineal glands of control and outside animals with the exception of HEX activity in the control animals. Significant acrophase differences in outside vs. control animals were noted in ACP (7.9 hr earlier, p < 0.001) and RON (9.8 hr later, p < 0.001). A significant drop in RON and HEX activity (p < 0.01 in both instances) was noted in association with the acute lights exposure in the morning to which control animals were exposed. The around-the-clock mean value of each enzyme was significantly lower in outside vs. control hamsters. These results demonstrate that environmental changes which provoke the pineal-mediated depression in gonadal activity also alter the activity of and shift the circadian rhythmicity of lysosomal enzymes in the pineal itself.