Bradykinin increases intracellular calcium levels in rat testis peritubular cells via the B 2 receptor subtype

RT–PCR and Western blots were used to detect bradykinin B 2 receptors in testis and isolated peritubular cells of pre‐pubertal rats. RT–PCR demonstrated expression of a single transcript, whereas Western blots showed up to three specific bands that were in accordance with the described native, glycosylated and dimeric form of B 2 receptor proteins, respectively. Fura‐2‐loaded peritubular cells responded with an instantaneous, linear and transient rise in [Ca 2+ ] i after adding bradykinin. Stimulation of cells with bradykinin concentrations between 1 μ M and 1 p M showed a dose dependent increase of [Ca 2+ ] i . The calcium response to bradykinin was diminished after stimulation of peritubular cells in calcium‐free buffer. After blocking the SERCA‐pumps by thapsigargin and subsequent stimulation with bradykinin, no rise of [Ca 2+ ] i was appreciated. Multiple stimulation of a single peritubular cell by local perfusion with a brief addition of BK (10 n M ) resulted in a fast and immediate response. However, the second and third stimuli had slower rise rates and diminished [Ca 2+ ] i peaks, showing desensitization of the kinin receptor. Addition of the bradykinin B 1 receptor agonist [des‐Arg 9 ]‐bradykinin (100 n M ) to Fura‐2‐loaded peritubular cells did not change the [Ca 2+ ] i . However, the B 2 receptor antagonist HOE 140 (100 n M ) strongly inhibited the bradykinin‐induced calcium response. We conclude that the bradykinin‐induced increase in [Ca 2+ ] i , in testicular peritubular cells is mediated by the stimulation of kinin receptors of the B 2 subtype. British Journal of Pharmacology (2003) 138 , 351–358. doi: 10.1038/sj.bjp.0705039