B2 bradykinin receptor mediates the stimulatory effect of bradykinin on rat germ cell proliferation in vitro
Summary.
The contribution of B1 and B2 bradykinin receptors to germ cell proliferation was studied by using in vitro organ cultures of testicular fragments of 3.5-day-old rats in the presence of 3H thymidine. Different combinations of agonists and antagonists of B1 and B2 receptors exerted differential mitogenic effect on pro-spermatogonial cells. Application of bradykinin (B2 receptor agonist) alone induced a threefold increase in germ cell labelling index compared with the control, whereas des-Arg9-bradykinin (B1 receptor agonist) caused weak stimulation (24%) on spermatogonial mitotic activity. The bradykinin-induced germ cell proliferation was significantly affected by B2 receptor antagonist (HOE-140) but not by B1 receptor antagonist. When B1 or B2 receptor antagonists were applied with des-Arg9-bradykinin, the germ cell labelling indices were nonsignificantly different compared with those of B1 receptor agonist only. The present findings suggest that B2 receptor is involved in mediating the stimulatory effect of bradykinin on germ cell proliferation and therefore bradykinin might be an important local testicular factor in the regulation of spermatogonial division and germ cell number.
