Yibchok-anun S, Cheng H, Abu-Basha E A, Ding J, Ioudina M, Hsu W H
Department of Biomedical Sciences, Iowa State University, Ames, IA 50011, USA.
Mol Cell Endocrinol. 2002 Jun 28;192(1-2):27-36. doi: 10.1016/s0303-7207(02)00115-6.
The mechanisms by which bradykinin (BK) increases glucagon release were investigated. BK (0.1-10 microM) increased Ca(2+) and glucagon release in clonal alpha-cells In-R1-G9. BK-induced glucagon release was lower in the absence than in the presence of extracellular Ca(2+), but it still increased glucagon release while Ca(2+) was stringently deprived. Depletion of intracellular Ca(2+) store with thapsigargin abolished both the BK-induced Ca(2+) peak and sustained plateau. Microinjection of heparin abolished BK-induced Ca(2+) release. Pertussis toxin (PTX) did not block BK-induced Ca(2+) increase or glucagon release. U-73122 (8 microM), a phospholipase C (PLC) inhibitor, abolished BK-induced increases in Ca(2+), but only reduced BK-induced glucagon release by 40%. A phospholipase D (PLD) inhibitor zLYCK reduced BK-induced glucagon release by 60%. The combination of U-73122 and zLYCK abolished BK-induced glucagon release. Both SK&F 96365, a receptor-operated Ca(2+) channel (ROC) blocker and nimodipine, an L-type Ca(2+) channel blocker, reduced BK-induced Ca(2+) increase and glucagon release. These findings suggest that BK increase glucagon release through a PTX-insensitive G protein and both Ca(2+)-dependent and -independent pathways. The Ca(2+)-dependent pathway is attributable to PLC activation. PLC catalyzes IP(3) formation, inducing Ca(2+) release from the endoplasmic reticulum, which, in turn, triggers Ca(2+) influx via both ROCs and L-type channels. PLD activation may be involved in Ca(2+)-dependent and/or -independent pathway.
研究了缓激肽（BK）增加胰高血糖素释放的机制。BK（0.1 - 10微摩尔）可增加克隆α细胞In-R1-G9中的[Ca(2+)]i及胰高血糖素释放。在无细胞外Ca(2+)时，BK诱导的胰高血糖素释放低于有细胞外Ca(2+)时，但在[Ca(2+)]i被严格剥夺时，它仍能增加胰高血糖素释放。毒胡萝卜素耗尽细胞内Ca(2+)储存可消除BK诱导的Ca(2+)峰值和持续平台期。显微注射肝素可消除BK诱导的Ca(2+)释放。百日咳毒素（PTX）不阻断BK诱导的[Ca(2+)]i增加或胰高血糖素释放。磷脂酶C（PLC）抑制剂U-73122（8微摩尔）可消除BK诱导的[Ca(2+)]i增加，但仅使BK诱导的胰高血糖素释放降低40%。磷脂酶D（PLD）抑制剂zLYCK使BK诱导的胰高血糖素释放降低60%。U-73122和zLYCK联合使用可消除BK诱导的胰高血糖素释放。受体操纵性Ca(2+)通道（ROC）阻滞剂SK&F 96365和L型Ca(2+)通道阻滞剂尼莫地平均可降低BK诱导的[Ca(2+)]i增加及胰高血糖素释放。这些发现表明，BK通过对PTX不敏感的G蛋白以及Ca(2+)依赖和非依赖途径增加胰高血糖素释放。Ca(2+)依赖途径归因于PLC激活。PLC催化IP(3)形成，诱导内质网释放Ca(2+)，进而通过ROC和L型通道触发Ca(2+)内流。PLD激活可能参与Ca(2+)依赖和/或非依赖途径。
