Retrieved or donated sperm cells are consequentially used to fertilize the oocyte under laboratory conditions. Depending on the count of usable living sperm cells two techniques are routinely performed. With sufficient count of living sperm cells (up to hundreds) standard in vitro fertilization (IVF) can be performed. The retrieved sperm cells are placed in a special dish containing a healthy oocyte and a special medium simulating natural conditions so the fertilization may occur. If there is only few sperm cells available after the retrieval, the intra cytoplasmic sperm injection (ICSI) is used. This technique uses just single sperm cell which is directly inserted by microneedle into the oocyte and the fertilization takes place.
We found that 221 genes and expressed sequence tags (ESTs) were differentially expressed in rat testes treated with estradiol compared to the control; the microarray data were confirmed by real time RT-PCR. Gene Ontology analysis revealed that a number of the differentially expressed genes are involved in androgen and xenobiotic metabolism, maintenance of cell cytoskeleton, endocytosis, and germ cell apoptosis. A total of 33 up-regulated genes and 67 down-regulated genes showed the presence of EREs. Flow cytometry showed that estradiol induced a significant decrease in 2n cells (somatic and germ cells) and 4n cells (pachytene spermatocytes) and a marked increase in the number of elongated and elongating spermatids.