Objective: To investigate molecular mechanisms of germ cell apoptosis induced by heat exposure in mice.
Design: Controlled laboratory study.
Setting: Departments of Urology and Biochemistry, Yamagata University School of Medicine, Yamagata, Japan.
Animal(s): Forty-four male B6D2F1 mice.
Intervention(s): Heat exposure, 43 degrees C for 15 minutes.
Main outcome measure(s): Testicular germ cell apoptosis (percentages of apoptotic tubules and apoptotic cells) was assessed by using DNA nick-end labeling, and expression of Bcl-2 family, Fas-FasL system, and p53 was evaluated by using Western analysis.
Result(s): Bilateral testicular weights decreased significantly from 3 days after heat exposure. Percentages of apoptotic tubules and apoptotic germ cells increased significantly from 1 day after heat exposure. There were no significant changes in the levels of Bcl-xl, Bad, and Bax after heat exposure. However, Bcl-2 expression level decreased significantly 7 days after heat exposure. In contrast, the expression level of Fas and p53 increased significantly from 1 day to 3 days after heat exposure, respectively. Expression level of FasL elevated significantly at days 1 and 2 but declined from day 3.
Conclusion(s): Germ cell apoptosis induced by heat exposure is mainly mediated by the Fas-FasL system.