Fellner Susan K, Arendshorst William
Dept. of Cell and Molecular Physiology, Univ. of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7545, USA.
Am J Physiol Renal Physiol. 2007 Jan;292(1):F175-84. doi: 10.1152/ajprenal.00050.2006. Epub 2006 Jun 20.
It is unknown if endothelin-A and -B receptors (ET(A)R and ET(B)R) activate the production of superoxide via NAD(P)H oxidase and subsequently stimulate the formation of cyclic adenine diphosphate ribose (cADPR) in afferent arterioles. Vessels were isolated from rat kidney and loaded with fura 2. Endothelin-1 (ET-1) rapidly increased cytosolic Ca(2+) concentration (Ca(2+)) by 303 nM. The superoxide dismutase mimetic tempol, the NAD(P)H oxidase inhibitor apocynin, and nicotinamide, an inhibitor of ADPR cyclase, diminished the response by approximately 60%. The ET(B)R agonist sarafotoxin 6c (S6c) increased peak Ca(2+) by 117 nM. Subsequent addition of ET-1 in the continued presence of S6c caused an additional Ca(2+) peak of 225 nM. Neither nicotinamide or 8-bromo- (8-Br) cADPR nor apocynin decreased the Ca(2+) response to S6c, but inhibited the subsequent Ca(2+) response to ET-1. The ET(B)R blockers BQ-788 and A-192621 prevented the S6c Ca(2+) peak and reduced the ET-1 response by more than one-half, suggesting an ET(B)R/ET(A)R interaction. In contrast, the ET(A)R blocker BQ-123 had no effect on the S6c Ca(2+) peak and obliterated the subsequent ET-1 response. ET-1 immediately stimulated superoxide formation (measured with TEMPO-9-AC, 68 arbitrary units) that was inhibited 95% by apocynin or diphenyl iodonium. S6c or IRL-1620 increased superoxide by 8% of that caused by subsequent ET-1 addition. We conclude that ET(A)R activation of afferent arterioles increases the formation of superoxide that accounts for approximately 60% of subsequent Ca(2+) signaling. ET(B)R activation appears to result in only minor increases in superoxide production. Nicotinamide and 8-Br-cADPR results suggest that ET-1 (and primarily ET(A)R) causes the activation of vascular smooth muscle cell-ADPR cyclase.
目前尚不清楚内皮素 -A和 -B受体（ET(A)R和ET(B)R）是否通过NAD(P)H氧化酶激活超氧化物的产生，进而刺激传入小动脉中环磷酸腺苷二磷酸核糖（cADPR）的形成。从大鼠肾脏分离血管并装载fura 2。内皮素 -1（ET-1）使胞质Ca(2+)浓度（Ca(2+)）迅速升高303 nM。超氧化物歧化酶模拟物tempol、NAD(P)H氧化酶抑制剂夹竹桃麻素和ADPR环化酶抑制剂烟酰胺使反应降低约60%。ET(B)R激动剂铃蟾毒素6c（S6c）使Ca(2+)峰值升高117 nM。在持续存在S6c的情况下随后添加ET-1导致Ca(2+)额外峰值为225 nM。烟酰胺或8-溴 -（8-Br）cADPR以及夹竹桃麻素均未降低对S6c的Ca(2+)反应，但抑制了随后对ET-1的Ca(2+)反应。ET(B)R阻滞剂BQ-788和A-192621阻止了S6c的Ca(2+)峰值，并使ET-1反应降低超过一半，提示存在ET(B)R/ET(A)R相互作用。相比之下，ET(A)R阻滞剂BQ-123对S6c的Ca(2+)峰值无影响，并消除了随后的ET-1反应。ET-1立即刺激超氧化物形成（用TEMPO-9-AC测量，68个任意单位），夹竹桃麻素或二苯基碘鎓可抑制95%。S6c或IRL-1620使超氧化物增加量为随后添加ET-1所引起增加量的8%。我们得出结论，传入小动脉的ET(A)R激活增加了超氧化物的形成，其占随后Ca(2+)信号传导的约60%。ET(B)R激活似乎仅导致超氧化物产生的轻微增加。烟酰胺和8-Br-cADPR的结果表明ET-1（主要是ET(A)R）导致血管平滑肌细胞ADPR环化酶的激活。
