BACKGROUND

The cystic fibrosis transmembrane conductance regulator (CFTR) plays a critical role in electrolyte and fluid transport in epithelial cells, and women with cystic fibrosis (CF), caused by CFTR gene mutations, have a higher incidence of infertility.

METHODS

In the present study, we investigated the expression of CFTR in porcine oviduct and its functional role in oviductal HCO₃^– secretion and embryo development with RT–PCR, western blot, patch-clamp, short-circuit current (I_sc), pH measurement and embryo culture.

RESULTS

RT–PCR and western blot analysis showed the expression of CFTR mRNA and protein in the oviduct with its localization demonstrated by immunohistochemstry. The whole-cell patch-clamp recording revealed a forskolin (FSK)-activated current with electrophysiological and pharmacological characteristics of CFTR. The I_sc measurement showed that FSK-stimulated an increase in the I_sc, which could be significantly reduced by CFTR inhibitor or removal of both CO₂ and HCO₃^–. pH measurement showed a FSK stimulated alkalization at the apical surface, which could be inhibited by CFTR inhibitor, indicating CFTR-mediated HCO₃^– secretion. Mouse embryo development from 2-cell to morula or blastocyst stage was significantly inhibited in the absence of HCO₃^– or when co-cultured with HCO₃^– secretion-deficient CFTR mutant cells as compared with the wild-type. RT–PCR, western blot and immunostaining showed the expression of soluble adenylate cyclase (sAC), the known HCO₃^– sensor, in embryos. Treatment with its inhibitors, 2-hydroxyestradiol and KH7, prevented the HCO₃^– dependent embryo development.

CONCLUSION

The present results suggest that CFTR-mediated oviductal HCO₃^– secretion may be vital for sAC-dependent early embryo development, a defect of which may contribute to the reduced fertility seen in women with CF.