Previously reported studies also used recombinant human leptin. Moreover, caution must be taken when comparing differ ent studies due to extensively different culture conditions dependent on the examined species. Again, our appar ently contraddictory results may be due to differences in semen source or fertilization procedures. In our study, ICSI procedure with directly fresh semen in Global medium was previousy tested as a reliable method to obtain equine embryos whereas in pigs, Kim et al. and Kun et al. used IVF and Somatic Cell Nuclear Transfer embryo in NCSU medium. in bovine, IVF in SOF medium was adopted. Our results demonstrated that Ob and Ob R proteins were detected in equine ICSI embryos throughout early cleav age stages. This finding is in agreement with previous observation in other species.

Moreover, leptin has been found to be secreted by various reproductive organs including placenta Inhibitors,Modulators,Libraries and ovary. Inhibitors,Modulators,Libraries Leptin has been reported to be expressed at high levels in mouse oocytes at all stages of follicular development whereas low expression levels were found Inhibitors,Modulators,Libraries in the mural granulosa, stroma, theca, and corpora lutea. Leptin receptor mRNA and protein were present in the mouse oocytes and preimplantation embryos. It has been reported that cultured human blastocysts secrete leptin, and the levels of leptin are significantly higher than those of arrested embryos. In human, leptin protein was localized in immature oocytes and in all stages of embry onic development. Recently, leptin protein Inhibitors,Modulators,Libraries was reported to be expressed in all stages of porcine IVF embryos.

This finding is also in agreement with our previous observation in equine oocytes. In oocytes at the GV stage, both Ob and Ob R were uniformly distrib uted throughout the ooplasm, but the intensity of reac tion was lower either in light weight mares or in fillies oocytes, than in oocytes of heavy weight mares. In matured oocytes, both Ob and Ob R were localized in the cortex and concentrated Inhibitors,Modulators,Libraries at one pole of the oocyte. This distribution was indipendent from the animal group and again with lower intensity in light mares and fillies. inhibitor order us Leptin and Ob R proteins in equine embryos were distrib uted according to the same cortical and cytoplasmic gran ule like distribution pattern in each blastomere. Interestingly, positive staining was also observed in the nuclei of 4 and 8 cell stage embryos. This finding is in agreement with previous observations of nuclear positiv ity in neurons in rat brain and perinuclear positivity in transfected Ob R expressing HeLa cells. This latter study examined the intracellular traffic of Ob R and reported that both isoforms of Ob R were observed in HeLa cells at three cellular localizations, the plasma mem brane, the peripheral cytoplasm and the perinuclear com partment.