Changes in expression and distribution of attractin in the testes of rats at different developmental stages.

Attractin (Atrn), an autosomal recessive gene, is widely expressed in the body and displays multiple physiological and pathological functions in different types of tissues. The objective of this study was to localize Atrn protein and mRNA in the testis and epididymis of rats at different stages of maturation. Testis and epididymidis samples were obtained from the following 5 groups of Sprague Dawley (SD) rats in different developmental stages: newborn (8 h after birth), prepubertal (5 days), pubertal (20 days), postpubertal (50 days) and mature (70 days). Tissues were fixed and prepared for indirect immunofluorescence, immunohistochemistry, in situ hybridization, confocal laser scanning microscopy and western blot assays. A polyclonal antiserum against mouse Atrn and oligonucleotide riboprobes were used in the above assays. At the different stages of maturation, Atrn protein and mRNA were both widely expressed in the rat testis, including Leydig cells, primitive spermatogonia, primary spermatocytes, spermatids, Sertoli and peritubular myoid cells. Staining of the Atrn protein was mainly located on the cell membrane and in the cell cytoplasm while Atrn mRNA was distributed in both the nucleus and cytoplasm. No immunopositive staining was detected in spermatozoa and epididymides. In the epididymis, comprised of the caput, corpus and cauda, there was no definitive immunopositive staining within the efferent ductules or epididymal ducts. Taken together, Atrn protein and mRNA are both expressed widely in the rat testis at different stages of maturation, which suggests that Atrn protein is involved and plays an important role in the development of the reproductive system. In addition, the rat testis has the ability to synthesize Atrn protein throughout sexual development.