Objective: To assess what the distributions of Fas system proteins are in normal rat testicular tissue; to assess whether there is a change in these distributions and in expression levels with experimentally-induced varicocele of 9, 11, and 13 weeks; and to assess whether there is a relationship between apoptosis and the Fas system in varicocele-induced rat testis. 

Design: Comparative and controlled study. 

Setting: University animal care and operation unit. 

Animal(s): Wistar male rats for experimental and control groups. 

Intervention(S): The control group underwent sham operation (n = 6). Rats in experimental groups underwent partial ligation of the renal vein to induce an experimental varicocele and then were killed at 9 (n = 6). 11 (n = 6), and 13 (n = 6) weeks after induction of varicoccle. 

Main Outcome Measure(s): Tissues were fixed mid processed for paraffin and Araldite embedding, and subsequently immunohistochemistry, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling, and transmission electron microscopy were performed. In addition, Western blotting was applied. 

Result(s): In control testis, we detected the expression of FasL in spermatids, interestingly at the progressing stages of acrosome formation and in the heads of the spermatozoa being released to lumen. Varicocele induction revealed a significant down-regulation of this protein, especially 11 weeks after the operation, without altering its distribution. Fas protein was present in cytoplasmic extrusions of the elongated spermatids and evidently in Leydig cells of the interstitial tissue. The expression of Fas protein was diminished after 11 weeks of varicocele induction, both in Leydig cells and in cytoplasmic extrusions. The decrease of Fas was significant in the 13-week-old varicocele group. whereas that of FasL was significant in the 11-week-old varicocele group. Compared with sham-operated animals, a minor increase in the number of apoptotic germ cells in varicocele groups was detected. 

Conclusion(s): Our results exposed other possible important roles of the Fas system in addition to than apoptosis in male reproduction. We suggest that therole of the Fas system needs further investigation both in animal models and in human male infertility.