OBJECTIVETo study the effects on the male reproduction in adult male rats and its mechanisms through simulated weightlessness using tail-suspension, in order to do a basic works of exploring the effects on human being's reproduction in outer space.

METHODSForty Spraque-Dawley adult male rats were randomly divided into four groups, two experimental groups and two control groups. Rats in the two experimental groups were tail-suspended for 14 d and 28 d respectively, then we examined the weight and morphology of testis, the quality and amount of sperm, also tested the serum hormone by radioimmunoassay and analyzed apoptosis rate of testicular cells by TUNEL in the experimental rats and control rats.

RESULTSAfter tail-suspension, the weight of testis, the sperm count and sperm motility significantly decreased (P <0.05), while the apoptosis rate of testicular cells and the amount of abnormal sperm markedly increased (P <0.05). The content of testosterone significantly decreased (P <0.05), but the contents of FSH and LH mildly increased (P > 0.05). These changes were not significant between two experimental groups (P > 0.05). In addition, the seminiferous tubules became atrophy with the reduction of the layers of seminiferous epithelium, and sperm amount in lumens of seminiferous tubules decreased in experimental groups. The above were more remarkable in the 28 d experimental group.

CONCLUSIONSimulating weightlessness has a harmful effect on reproduction of adult male rats. These may be caused by inducing apoptosis. The blocking apoptosis of testicular cells may be useful in improving the harmful effect.