RT Journal Article SR Electronic T1 Mechanisms of Bradykinin-Induced Insulin Secretion in Clonalbeta Cell Line RINm5F JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 1247 OP 1252 VO 282 IS 3 A1 Yang, Chi A1 Lee, Bumsup A1 Chen, Ter-Hsin A1 Hsu, Walter H. YR 1997 UL http://jpet.aspetjournals.org/content/282/3/1247.abstract AB We investigated the mechanisms underlying bradykinin (BK)-induced rise in intracellular Ca++ concentration [Ca++]i and insulin secretion using clonal beta cell line RINm5F. Incubation with a range of concentrations of BK increased in concentration-dependent manners both insulin secretion (BK of 10 nM to 10 μM) and [Ca++]i (BK of 100 nM to 100 μM). In Ca++-containing medium, BK (1 μM) induced a biphasic [Ca++]i rise, which was characterized by a Ca++ peak and a sustained Ca++ phase. In the Ca++-free medium, BK failed to increase insulin secretion and induced only a Ca++ peak without the sustained Ca++ phase. Thapsigargin (1 μM), an inhibitor of the Ca++ pump in the endoplasmic reticulum, abolished the Ca++ peak and the sustained phase. Nimodipine (1 μM), a voltage-dependent Ca++ channel blocker, abolished the BK-induced sustained Ca++ phase and inhibited BK-induced insulin release. The BK1 receptor agonist des-Arg9-BK (1 μM) did not change either [Ca++]i or insulin secretion. Both the BK-induced insulin secretion and rise in [Ca++]i were inhibited by a selective BK2 receptor antagonist, HOE 140 (3.3–100 nM), in concentration-dependent manners but were not by a BK1 receptor antagonist des-Arg9,Leu8-BK (1 μM). Pretreatment with pertussis toxin (0.1 μg/ml) did not block the BK-induced insulin secretion or increase in [Ca++]i. U-73122 (4, 6 and 8 μM), a phospholipase C inhibitor, antagonized both the BK-induced insulin secretion and the increase in [Ca++]i in a concentration-dependent and parallel manner. BK increased intracellular concentrations of inositol-1,4,5-trisphosphate (IP3). Neither (p-amylcinnamoyl)anthranilic acid (100 μM), a phospholipase A2 inhibitor, nor NG-nitro-l-arginine methylester (100 μM), a nitric oxide synthase inhibitor, inhibited these effects of BK. Taken together, these findings suggested that in betacells, BK activates BK2 receptors, which, in turn, activate a pertussis toxin-insensitive G protein. The G protein couples to phospholipase C, which promotes the formation of IP3 and diacylglycerol. IP3releases [Ca++]i from the intracellular Ca++ store, probably the endoplasmic reticulum, which triggers Ca++ influxvia voltage-dependent Ca++ channels and thus increases insulin secretion. The American Society for Pharmacology and Experimental Therapeutics