Vamos S, Welling L W, Wiegmann T B
Renal Section, Veterans Affairs Medical Center, Kansas City, MO 64128, USA.
J Lab Clin Med. 1995 Apr;125(4):470-8.
Bradykinin (BK) induces intracellular calcium ([Ca2+]i) release in Madin-Darby canine kidney (MDCK) cells. During long-term continuous BK exposure, cells become desensitized and fail to respond to a new BK stimulus. We used a protocol of repeated short-term BK addition and removal. MDCK cells were loaded with the Ca-indicator indo-1 and were exposed to BK (100 nmol/L) for 10 seconds, followed by BK removal. This cycle was repeated four to eight times while [Ca2+]i was continuously recorded. In a Ca-free bath, the cells gradually became completely desensitized to repeated BK stimuli. In the presence of 1 mmol/L or 10 mmol/L Cae, however, repeated addition of BK caused repeated [Ca2+]i transients with partial decrease of peak heights (327 and 436 nmol/L delta[Ca2+]i final) (partial desensitization). Repeated BK stimuli also led to partial desensitization (70% to 85%) to adenosine triphosphatase and carbachol (heterologous desensitization). BK also reduced peak thapsigargin response (70%), consistent with partial depletion of endoplasmic reticulum Ca pools. Our results show that MDCK cells maintain their sensitivity to BK during repeated short-term BK exposures. Available Ca3 plays a major role in modulating the degree of cellular responsiveness.
缓激肽（BK）可诱导犬肾近曲小管上皮细胞（MDCK）释放细胞内钙（[Ca2+]i）。在长期持续暴露于BK的过程中，细胞会出现脱敏现象，不再对新的BK刺激产生反应。我们采用了反复短期添加和去除BK的实验方案。将MDCK细胞用钙指示剂indo-1进行负载，然后暴露于100 nmol/L的BK中10秒，随后去除BK。这个循环重复4至8次，同时持续记录[Ca2+]i。在无钙浴中，细胞逐渐对反复的BK刺激完全脱敏。然而，在存在1 mmol/L或10 mmol/L Ca2+的情况下，反复添加BK会导致反复的[Ca2+]i瞬变，且峰值高度部分降低（最终Δ[Ca2+]i分别为327和436 nmol/L）（部分脱敏）。反复的BK刺激还导致对三磷酸腺苷酶和卡巴胆碱产生部分脱敏（70%至85%）（异源脱敏）。BK还降低了毒胡萝卜素的峰值反应（70%），这与内质网钙池的部分耗竭一致。我们的结果表明，MDCK细胞在反复短期暴露于BK期间保持对BK的敏感性。细胞外可用钙在调节细胞反应程度中起主要作用。
