Kawabata A, Kuroda R, Kuroki N, Nishikawa H, Kawai K, Araki H
Department of Pathophysiology & Therapeutics, Faculty of Pharmaceutical Sciences, Kinki University, Higashi-Osaka, Japan.
Life Sci. 2000 Oct 6;67(20):2521-30. doi: 10.1016/s0024-3205(00)00835-3.
Activation of protease-activated receptor-1 (PAR-1) produces a dual action, apamin-sensitive relaxation followed by contraction, in the rat duodenal smooth muscle, which is partially dependent on activation of L-type Ca2+ channels, protein kinase C (PKC) or tyrosine kinase (TK), and resistant to tetrodotoxin. The present study further characterized the PAR-1-mediated duodenal responses. Removal of extracellular Ca2+ as well as SK&F96365 reduced the contraction due to the PAR-1 agonist TFLLR-NH2 (TFp-NH2) by 60-80% that was similar to the extent of the inhibition by nifedipine. Lowering of the extracellular Na+ concentration, but not IAA-94, a Cl- channel inhibitor, reduced both the PAR-1-mediated contraction and relaxation by about 50%. U73122, a phospholipase C (PLC) inhibitor, or wortmannin, a phosphatidyl inositol 3'-kinase (PI3K) inhibitor, significantly reduced the PAR-1-mediated contraction, but not the relaxation, by itself, as the PKC inhibitor GF109203X and the TK inhibitor genistein did. U73122 or wortmannin, like GF109203X, when applied in combination with genistein, significantly reduced the PAR-1-mediated relaxation. The relaxation was resistant to antagonists of PACAP receptors, VIP receptors and P2 purinoceptors. Thus, the PAR-1-mediated contraction is considered to be dependent on intracellular and extracellular Ca2+, the influx of the latter being induced through activation of L-type Ca2+ channels triggered by the enhanced Na+ permeability, and that PLC and PI3K, in addition to PKC and TK, are involved in the PAR-1-mediated dual responses. Furthermore, non-adrenergic, non-cholinergic nerve neurotransmitter candidates that may modulate K+ channels do not appear to contribute to the relaxation by PAR-1 activation.
蛋白酶激活受体-1（PAR-1）的激活在大鼠十二指肠平滑肌中产生双重作用，先是对蜂毒明肽敏感的舒张，随后是收缩，这部分依赖于L型钙通道、蛋白激酶C（PKC）或酪氨酸激酶（TK）的激活，且对河豚毒素有抗性。本研究进一步对PAR-1介导的十二指肠反应进行了特征描述。去除细胞外钙以及SK&F96365使PAR-1激动剂TFLLR-NH2（TFp-NH2）引起的收缩降低了60%-80%，这与硝苯地平的抑制程度相似。降低细胞外钠浓度，但不是氯离子通道抑制剂IAA-94，使PAR-1介导的收缩和舒张均降低了约50%。磷脂酶C（PLC）抑制剂U73122或磷脂酰肌醇3'-激酶（PI3K）抑制剂渥曼青霉素本身显著降低了PAR-1介导的收缩，但不影响舒张，蛋白激酶C抑制剂GF109203X和酪氨酸激酶抑制剂染料木黄酮也是如此。U73122或渥曼青霉素与GF109203X一样，与染料木黄酮联合应用时，显著降低了PAR-1介导的舒张。该舒张对垂体腺苷酸环化酶激活肽（PACAP）受体、血管活性肠肽（VIP）受体和P2嘌呤受体的拮抗剂有抗性。因此，PAR-1介导收缩被认为依赖于细胞内和细胞外钙，后者的内流是通过增强的钠通透性激活L型钙通道诱导的，并且除了PKC和TK外，PLC和PI3K也参与了PAR-1介导的双重反应。此外，可能调节钾通道的非肾上腺素能、非胆碱能神经递质候选物似乎对PAR-1激活引起的舒张没有作用。
