Effect of aging and dietary restriction on rat testicular germ cell apoptosis

The purpose of this study was to determine whether apoptotic cell death of rat testicular germ cells varies with increased age or with dietary restric tion. Slide-mounted cross-sections of formalin-fixed testis from 4-, 13-, a nd 23-month-old adlibitum-fed and 40% dietary-restricted male F344 rats wer e used in an in situ assay for apoptotic germ cells. Results show that in a d-libitum-fed rats, increased age caused a significant increase in the perc entage of seminiferous tubules containing apoptotic cells, but a significan t decrease in the number of apoptotic cells per apoptosis-positive tubule. In the 23-month-old rats, dietary restriction significantly increased both the percentage of apoptotic positive tubules and the number of apoptotic ce lls per apoptosis-positive tubule above ad-libitum-fed values. Both ad-libi tum and diet-restricted groups demonstrated a decrease in the percentage of apoptotic spermatogonia concomitant with a significant increase in the per centage of apoptotic primary spermatocytes with advanced age. The significa nt age-related increase in total numbers of apoptotic germ cells may reflec t elimination of defective germ cells, which occurs with increased frequenc y in advanced age. Dietary restriction may induce enhanced screening agains t defective germ cells above that seen in the ad-libitum-fed rats. These re sults have potential implications in aging studies as well as research invo lving perturbation of normal germ cell homeostasis.