Expression and location of the bradykinin B2 receptor in rat testis

To investigate the possible role of the local tissue kallikrein-kinin system in spermatogenesis, we analyzed gene expression and cellular distribution of the bradykinin subtype-2 receptor (B(2) receptor) in the rat testis. Reverse transcription-polymerase chain reaction revealed B(2) receptor expression in testis and primary cultures of Sertoli cells and peritubular cells isolated from immature and mature rats. In situ hybridization of the B(2)-receptor mRNA showed intense labeling of cells on the base of the seminiferous tubule, whereas the autoradiographic signals gradually decreased toward the lumen. Immune histochemistry using testicular sections of pubertal and adult rats showed specific staining for the B(2)-receptor protein in cells of the adluminal compartment of the seminiferous tubules, especially on pachytene spermatocytes and spermatids. This immunostaining varied with the stages of the seminiferous cycle. The receptor protein was also observed on peritubular cells of pubertal rats. In conclusion, we demonstrated a stage-specific expression of the bradykinin B(2) receptor in different cells of the seminiferous tubules of the rat testis. The results point to a possible function of the tissue kallikrein-kinin system in the local regulation of spermatogenesis.