Cystic fibrosis is the most frequent autosomal recessive disease in the 
Caucasian population, with an incidence of 1:2500 newborn and a frequency of 
1:25. The associated gene is Cystic Fibrosis Transmembrane Conductance Regulator 
(CFTR) and it encodes the CFTR protein that functions as a chloride (Cl(-)) 
channel. It is found in the apical membrane of exocrine epithelial cells, 
responsible for the regulation of the movement of water and solutes through 
biological membranes. To our knowledge, there are no studies on protein 
localization in the different cell types of the seminiferous epithelium with 
different pathologies. The aim of the present study was to analyze the 
expression of the CFTR protein in the human seminiferous epithelium of infertile 
males with different pathologies. CFTR protein expression was studied by 
immunohistochemistry in paraffin sections of testicular biopsies of six 
infertile men: Sertoli cell only syndrome, maturation arrest, secondary 
obstructive azoospermia, primary obstructive azoospermia due to congenital 
bilateral absence of the vas deferens (CBAVD), severe oligozoospermia, and 
retrograde ejaculation. All cell types of the seminiferous epithelium were 
studied: Sertoli cells, spermatogonia, primary spermatocytes at the 
leptotene/zygotene and at the pachytene stages, secondary spermatocytes, round, 
elongating and elongated spermatids, and spermatozoa. With the exception of 
sperm, all cells were labeled in the cytoplasm and in the cytoplasmic membrane. 
In the patient with CBAVD labeling was light at the cell membrane and absent in 
the cytoplasm of Sertoli cells and diploid germ cells. Generally, labeling was 
stronger after the diploid stage, which is probably related to cell volume 
reduction during spermiogenesis. The results obtained also suggest that the CFTR 
protein may impact CBAVD spermatogenesis and other pathologies.