Yanai K, Maeyama K, Nakahata N, Nakanishi H, Watanabe T
Department of Pharmacology I, Tohoku University School of Medicine, Sendai, Japan.
Naunyn Schmiedebergs Arch Pharmacol. 1992 Jul;346(1):51-6. doi: 10.1007/BF00167570.
Intracellular free Ca2+ concentration ([Ca2+]i) was monitored in monolayer of 1321 N1 astrocytoma cells by using a fluorescent Ca2+ indicator fura-2. Endothelin-1 (ET-1), endothelin-2 (ET-2), and sarafotoxin Sb6 (SRTX) increased [Ca2+]i from 56 +/- 6 nM to 360 +/- 82, 120 +/- 51, 143 +/- 29 nM, respectively, immediately after their addition to the perfusate with maximum response of more than 0.1 microM of peptides. Endothelin-3 (less than 1 microM) did not affect [Ca2+]i. The increase in [Ca2+]i in response to either ET-1, ET-2, or SRTX could be almost completely inhibited by pretreating cells with ET-1 or ET-2. The homologous desensitization of [Ca2+]i induced by ETs and SRTX is in good agreement with their affinity toward an ETA receptors. The responses in [Ca2+]i by ETs and SRTX were not affected in the desensitized state induced by the pretreatment of histamine in the presence of extracellular Ca2+. However, the response in [Ca2+]i by ETs and SRTX were reduced in the desensitized state induced by pretreatment of histamine in the absence of extracellular Ca2+. These results indicate that depletion of the intracellular Ca2+ stores is responsible for the heterologous desensitization between ETs and histamine.
通过使用荧光钙指示剂fura - 2监测1321 N1星形细胞瘤细胞单层中的细胞内游离钙浓度（[Ca2+]i）。内皮素 - 1（ET - 1）、内皮素 - 2（ET - 2）和沙拉毒素Sb6（SRTX）在加入灌流液后立即将[Ca2+]i分别从56±6 nM升高至360±82、120±51、143±29 nM，当肽浓度超过0.1 microM时达到最大反应。内皮素 - 3（小于1 microM）不影响[Ca2+]i。用ET - 1或ET - 2预处理细胞几乎可以完全抑制ET - 1、ET - 2或SRTX引起的[Ca2+]i升高。ETs和SRTX诱导的[Ca2+]i同源脱敏与其对ETA受体的亲和力高度一致。在细胞外钙存在的情况下，组胺预处理诱导的脱敏状态下，ETs和SRTX引起的[Ca2+]i反应不受影响。然而，在细胞外钙不存在的情况下，组胺预处理诱导的脱敏状态下，ETs和SRTX引起的[Ca2+]i反应降低。这些结果表明细胞内钙库的耗竭是ETs和组胺之间异源脱敏的原因。
