Participation of the oviductal s100 calcium binding protein G in the genomic effect of estradiol that accelerates oviductal embryo transport in mated rats

Background Mating changes the mechanism by which E2 regulates oviductal egg transport, from a non-genomic to a genomic mode. Previously, we found that E2 increased the expression of several genes in the oviduct of mated rats, but not in unmated rats. Among the transcripts that increased its level by E2 only in mated rats was the one coding for an s100 calcium binding protein G (s100g) whose functional role in the oviduct is unknown. Methods Herein, we investigated the participation of s100g on the E2 genomic effect that accelerates oviductal transport in mated rats. Thus, we determined the effect of E2 on the mRNA and protein level of s100g in the oviduct of mated and unmated rats. Then, we explored the effect of E2 on egg transport in unmated and mated rats under conditions in which s100g protein was knockdown in the oviduct by a morpholino oligonucleotide against s100g (s100g-MO). In addition, the localization of s100g in the oviduct of mated and unmated rats following treatment with E2 was also examined. Results Expression of s100g mRNA progressively increased at 3-24 h after E2 treatment in the oviduct of mated rats while in unmated rats s100g increased only at 12 and 24 hours. Oviductal s100g protein increased 6 h following E2 and continued elevated at 12 and 24 h in mated rats, whereas in unmated rats s100g protein increased at the same time points as its transcript. Administration of a morpholino oligonucleotide against s100g transcript blocked the effect of E2 on egg transport in mated, but not in unmated rats. Finally, immunoreactivity of s100g was observed only in epithelial cells of the oviducts of mated and unmated rats and it was unchanged after E2 treatment. Conclusions Mating affects the kinetic of E2-induced expression of s100g although it not changed the cellular localization of s100g in the oviduct after E2. On the other hand, s100g is a functional component of E2 genomic effect that accelerates egg transport. These findings show a physiological involvement of s100g in the rat oviduct.