Expression of the cystic fibrosis transmembrane conductance regulator in rat spermatids: implication for the site of action of antispermatogenic agents

To establish whether cystic fibrosis transmembrane conductance regulator (C FTR) is functionally expressed in the testis, we subjected spermatogenic ce lls from rat testes to analysis of CFTR mRNA, protein and channel activity. CFTR mRNA was detected in the testes of mature but not immature rats using reverse transcription-polymerase chain reaction analysis. Western blot ana lysis performed with a CFTR specific antibody revealed immunoreactivity in the membrane extract of spermatogenic cells. Immunohistochemical studies lo calized CFTR in round and elongated spermatids, but not in the fully develo ped spermatozoa. Using a whole-cell patch clamp technique, we recorded an i nward current activated by intracellular cAMP (100 mu mol/l) in round sperm atids. The current displayed a linear IN relationship and was inhibited by diphenylamine-2-carboxylate (DPC), a chloride channel blocker. Transfection of the rat germ cell CF, TR cDNA into human embryonic kidney (HEK) 293 cel ls caused the expression of a cAMP-activated chloride current with CFTR cha racteristics. The current was completely blocked by the antispermatogenic a gents 1-(2,4-dichlorobenzyl)-indazole-3-carboxylic acid, lonidamine (500 mu mol/l) and 1-(2,4-dichlorobenzyl)-indazole-3-acrylic acid, AF2785 (250 mu mol/l). These results taken together provide evidence that CFTR is differen tially expressed in spermatids during spermiogenesis. We speculate that CFT R may interact with aquaporin to bring about cytoplasmic volume contraction which is an essential feature of spermiogenesis.