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Intracellular pH regulation in human Sertoli cells: role of membrane transporters

¹ UMIB, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, L. Prof. Abel Salazar, 2, 4099-003 Porto, Portugal² Laboratório de Biologia Celular, ICBAS-UP, 4099-003 Porto, Portugal³ Departamento de Genética, FM-UP, 4200-319 Porto, Portugal⁴ REQUIMTE, Departamento de Química, FCT-UNL, 2829-516 Caparica, Portugal⁵ Laboratório de Fisiologia Geral, ICBAS-UP, 4099-003 Porto, Portugal

Correspondence should be addressed to P F Oliveira who is now at Laboratório de Fisiologia dos Gâmetas e Transporte Iónico, ICBAS, LNIV (ala H), Rua dos Lagidos, Lugar da Madalena, 4485-655 Vairão, Vila do Conde, Portugal; Email: transp.bio{at}mail.icav.up.pt

Sertoli cells are responsible for regulating a wide range of processes that lead to the differentiation of male germ cells into spermatozoa. Intracellular pH (pHi) is an important parameter in cell physiology regulating namely cell metabolism and differentiation. However, pHi regulation mechanisms in Sertoli cells have not yet been systematically elucidated. In this work, pHi was determined in primary cultures of human Sertoli cells. Sertoli cells were exposed to weak acids, which caused a rapid acidification of the intracellular milieu. pHi then recovered by a mechanism that was shown to be particularly sensitive to the presence of the inhibitor DIDS (4,4'-diisothiocyanostilbene disulfonic acid). In the presence of amiloride and PSA (picrylsulfonic acid), pHi recovery was also significantly affected. These results indicate that, in the experimental conditions used, pHi is regulated by the action of an Na⁺-driven HCO₃^–/Cl^– exchanger and an Na⁺/HCO₃^– co-transporter and also by the action of the Na⁺/H⁺ exchanger. On the other hand, pHi recovery was only slightly affected by concanamycin A, suggesting that V-Type ATPases do not have a relevant action on pHi regulation in human Sertoli cells, and was independent of the presence of bumetanide, suggesting that the inhibition of the Na⁺/K⁺/Cl^– co-transporter does not affect pHi recovery, not even indirectly via the shift of ionic gradients. Finally, pHi was shown to be sensitive to the removal of external Cl^–, but not of Na⁺ or K⁺, evidencing the presence of a membrane Cl^–-dependent base extruder, namely the Na⁺-independent HCO₃^–/Cl^– exchanger, and its role on pHi maintenance on these cells.