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- Aquaporins as molecular partners of CFTR in Sertoli CellsPublication . Jesus, Tito Miguel Boléo Teles de; Oliveira, Pedro Fontes; Alves, Marco Aurélio GouveiaThe establishment of the adequate ionic and water environment within the lumen of the seminiferous tubules (SFT), with the secretion of its numerous components, is vital for the normal occurrence of spermatogenesis. Specific transporters for HCO3 -, a mobile physiological buffer that plays a crucial role in the maintenance of intracellular and extracellular pH, have been described in the SFTs. Additionally, water transporters known as Aquaporins have been identified in the SFT, being most probably involved in the secretion of the luminal fluid. Within the SFT, Sertoli cells (SCs) play a crucial role in the establishment of the luminal fluid. Thus, it is imperative to unravel HCO3 - and water transport dynamics in SCs to identify and counteract possible alterations related with reduced male fertility caused by pathological conditions associated with altered water and HCO3 - transport, such as cystic fibrosis (CF). So the first objective of this work was to evaluate mRNA and protein expression of the cystic fibrosis transmembrane conductance regulator (CFTR) in SCs, by RT-PCR and immunoblot, respectively, using primary cultures obtained from 20-day old rats. The second objective was to identify the expression of specific aquaporin (AQP) isoforms (AQP0-AQP9), using a similar approach. Finally, the third objective was to investigate the possible physical interaction between CFTR and specific AQP isoforms in SCs, using the co-immunoprecipitation technique. We were able to detect in cultured SCs both, the expression of mRNA transcripts and of proteins of the bicarbonate transporter CFTR and AQP isoforms 4, 8 and 9. The presence of the proteins AQP6 and AQP7 was also detected although no mRNA transcript correspondent to these AQPs isoforms was observed. Furthermore, in the present study, we observed a direct interaction between AQP4 and CFTR, using the co-immunoprecipitation technique. Thus, in the SFTs, ion and water secretion, driven by specific SCs membrane transporters, is an important step that helps to control the final osmolarity and fluidity of the luminal content. Our results allowed us to identify the expression of various AQP isoforms in rat SCs, particularly AQP4, AQP8 and AQP9, highlighting the importance of water transport in these cells and suggesting that the different AQPs may serve more than one particular function. Additionally, our results indicate that AQP4 physically interacts with CFTR, evidencing a possible role for this HCO3 - transporter in the regulation of AQPs and water homeodynamics in rat SCs. Defective water transport might be the leading cause of the obstructive pathologies, followed by atrophy and infertility, which are observed in men with CF. So it is possible that disruption of a functional complex involving AQP4 and CFTR might contribute to the pathogenesis of male infertility/subfertility in CF.