| Abstract: | Malate dehydrogenase activity and soluble protein content in testes from rats exposed to a 14:00 h light:10:00 h dark photoperiod, have been determined every two or four hours over a 24 hour period in 5, 15, 25 and 120 day-old rats. By using the Cosinor method, the ontogeny of an unimodal rhythm was studied for MDH activity and soluble protein content in testis. In 5 and 15 day-old rats, the MDH acrophases were recorded around 19:00 h and 17:00 h, respectively. Rats aged 25 and 110 days showed the MDH acrophases during the dark period. An inversion of the MDH circadian rhythms was detected in 25 day-old compared to those of 5 and 15 day-old rats. An inversion of the protein circadian rhythm was also detected at 15 days compared to that at 5 days. These inversions persist in the adult rats. The amplitude of the MDH and protein rhythms reached the lowest value in adulthood. The mean daily value of testicular MDH increased between day 5 and 15, decreasing at day 35 and remaining unchanged until adulthood. The variation of malate dehydrogenase activity, soluble protein content levels, and the circadian rhythm parameters during the maturation process may be related to gonad development. |
