Effect of Melatonin on Expression of Apoptosis Regulator Proteins Bcl-2 and Bad in Ovarian Follicular Apparatus after High Temperature Exposure.

Expression of proapoptotic Bad and antiapoptotic Bcl-2 proteins in ovarian follicular apparatus of Wistar rats was evaluated on days 3, 7, and 14 after single experimental hyperthermia (EH) followed by therapeutic correction with subcutaneous melatonin (0.1 mg) dissolved in 0.2 ml physiological saline (PS) injected daily for 3 days. Duration of EH was less than 17 min; it was terminated when the rectal temperature attained 43.5°C. In acute posthyperthermia period (on experimental day 3), Bcl-2 and Bad expression area in folliculocytes of the experimental (EH+melatonin) and reference rats simultaneously increased in comparison with the corresponding values in control rats. At this, Bcl-2/Bad ratio of expression areas in experimental and reference rats did not differ from the control level. During the recovery period (on posthyperthermia day 7), Bad protein expression area significantly decreased in experimental rats resulting in elevation of Bcl-2/Bad ratio in comparison with control and reference groups on days 3 and 7. On day 14, Bcl-2 and Bad expression areas and Bcl-2/Bad ratio restored in experimental animals to the corresponding values assessed in control and reference groups. Thus, melatonin produced no effect on Bcl-2/Bad protein expression ratio during acute posthyperthermia period, but reduced the expression area of proapoptotic Bad protein and increased Bcl-2/Bad ratio on posthyperthermia day 7. Thus, melatonin can inhibit apoptosis via mitochondrial pathway in ovarian follicles on posthyperthermia day 7.