SERTOLI-CELL EXPRESSION OF THE CYSTIC-FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR

Mutations of the cystic fibrosis transmembrane conductance regulator ( CFTR) gene have been associated with a number of male reproductive pro blems, including testis abnormalities and a reduction in germ cell qua lity and number. To establish at least one site of functional CFTR exp ression in the testis, we subjected cultured Sertoli cells to analysis of message, protein, and channel activity for CFTR. With reverse tran scription-polymerase chain reaction, we obtained evidence for the pres ence of CFTR RNA when CFTR primers were used with RNA from cultured Se rtoli cells. Western analysis performed with both anti-R and anti-C do main CFTR antibodies revealed immunoreactive material in extracts from primary Sertoli cell cultures that seemed consistent with CFTR previo usly identified in other cells and tissues. This led us to perform mor e detailed studies using the whole cell arrangement of the patch-clamp technique. Application of the membrane-soluble cAMP analog, 8-chlorop henylthio-cAMP, resulted in the activation of a Cl- current that displ ayed a permeability sequence of Br- > I- greater than or equal to Cl- and was blocked by diphenylamine-2-carboxylate and glibenclamide. In a ddition, a 13-pS conductance Cl- channel was measured in excised membr ane patches exposed to the catalytic subunit of protein kinase A. When taken together, our findings of evidence of CFTR message, immunoreact ive material that appeared consistent with CFTR, and Cl- channels with properties similar to those reported for CFTR provide strong evidence that Sertoli cells express a functional CFTR-like protein. The presen ce of CFTR in these cells may be needed to maintain the specific nutri tional and fluid balance in the seminiferous tubule that is vital for normal spermatogenesis.