Immunolocalization of glial cell-derived neurotrophic factor (GDNF) and its receptor GFR-alpha1 in varicocele-induced rat testis

The aim of the study was to determine the immunolocalisation of glial cell-derived neurotrophic factor (GDNF) and its receptor (GFRalpha1) in testicular dysfunction induced by experimental left varicocele. Male Wistar rats were divided randomly into two groups: a varicocele-induced group and a sham-operated group for 9, 11 and 13 weeks (each group n=6). After orchiectomy, part of the left testis from each animal was fixed, processed and embedded in paraffin wax for immunohistochemistry and the other part was fixed for ultrastructural investigations. GDNF immunoreactivity was localized in the interstitial space in Leydig cell cytoplasm and there was no significant difference (P=0.5) between the varicocele-induced groups at the various time points. GFRalpha1 localization was perinuclear in spermatids and cytoplasmic in Leydig cells. The decrease of GFRalpha1 immunoreactivity was significant (P=0.001) in varicocele-induced testis at 13 weeks when compared with the age-matched sham group. This is the first study to describe the immunolocalization patterns of GDNF and GFRalpha1 in a rat model of varicocele. Although there was no change in GDNF labelling at the different time points after varicocele, GFRalpha1 was significantly decreased in the 13-week group. Distribution of GDNF and its receptor GFRalpha1 in normal and varicocele-induced rat testes suggests both autocrine and paracrine regulation of spermatogenesis.