Quinn S J, Enyedi P, Tillotson D L, Williams G H
Department of Physiology, Boston University School of Medicine, Massachusetts 02118.
Endocrinology. 1990 Aug;127(2):541-8. doi: 10.1210/endo-127-2-541.
Cytosolic calcium (Cai) responses to arginine vasopressin (AVP) and angiotensin-II (Ang II) were examined in single rat adrenal zona glomerulosa (ZG) cells by monitoring fura-2 fluorescence with microspectrofluorimetry. ZG cells displayed dose-dependent Cai responses to a wide range of AVP and Ang II concentrations, starting from a threshold of 1 nM for AVP and less than 5 pM for Ang II. A dose-dependent delay of the onset of the Cai response was observed with both hormones. The response delay for Ang II was consistently briefer than that for the same concentration of AVP, showing a 2-3 log unit separation in the dose-response relations. After the delay, cells typically responded with an abrupt increase in Cai, which peaked within 15 sec. The amplitude of the peak Cai rise showed little dependency on AVP or Ang II concentration. At most AVP concentrations, the response consisted of Cai oscillations, with apparent fusion of these Cai oscillations at the highest AVP concentrations (1-0.1 microM). Similar oscillatory behavior was found with stimulations by much lower Ang II concentrations (0.5 nM to 5 pM). There appeared to be a 2-3 log unit shift in the sensitivity toward AVP and Ang II when Cai responses were compared. Sixty percent of ZG cells were responsive to AVP, while more than 90% displayed an elevation of Cai with Ang II. The Cai and steroid responses to 100 nM AVP and 100 pM Ang II were compared, since these two doses are reported to stimulate the phosphoinositide system to a similar extent. Individual ZG cells tested with both hormones responded with equivalent peak Cai changes, but a slightly longer response delay for AVP. The mean Cai response and aldosterone production for each secretagogue displayed parallel kinetics during 30-min stimulations. After initial oscillations, the Cai response returned to control values within 15 min of 100 nM AVP application. Likewise, the steroid output was transient. In contrast, 100 pM Ang II produced maintained Cai oscillations as well as a sustained and substantially greater aldosterone production for the same period of application. In conclusion, the disparate steroidogenic effects of AVP and Ang II appear to result from distinctly different Cai responses elicited during maintained secretagogue stimulation.
通过显微分光荧光测定法监测fura - 2荧光，在单个大鼠肾上腺球状带（ZG）细胞中检测了细胞溶质钙（Cai）对精氨酸加压素（AVP）和血管紧张素II（Ang II）的反应。ZG细胞对广泛的AVP和Ang II浓度表现出剂量依赖性的Cai反应，AVP的阈值为1 nM，Ang II的阈值小于5 pM。两种激素均观察到Cai反应起始的剂量依赖性延迟。Ang II的反应延迟始终比相同浓度的AVP短，在剂量反应关系中显示出2 - 3个对数单位的差异。延迟后，细胞通常以Cai的突然增加做出反应，并在15秒内达到峰值。峰值Cai升高的幅度对AVP或Ang II浓度的依赖性很小。在大多数AVP浓度下，反应包括Cai振荡，在最高AVP浓度（1 - 0.1 microM）时这些Cai振荡明显融合。在低得多的Ang II浓度（0.5 nM至5 pM）刺激下也发现了类似的振荡行为。比较Cai反应时，对AVP和Ang II的敏感性似乎有2 - 3个对数单位的变化。60%的ZG细胞对AVP有反应，而超过90%的细胞在Ang II作用下Cai升高。比较了Cai和类固醇对100 nM AVP和100 pM Ang II的反应，因为据报道这两种剂量对磷酸肌醇系统的刺激程度相似。用两种激素测试的单个ZG细胞的峰值Cai变化相当，但AVP的反应延迟略长。在30分钟的刺激过程中，每种促分泌素的平均Cai反应和醛固酮产生呈现平行动力学。在应用100 nM AVP后，最初的振荡后，Cai反应在15分钟内恢复到对照值。同样，类固醇输出是短暂的。相比之下，100 pM Ang II在相同的应用时间段内产生持续的Cai振荡以及持续且显著更高的醛固酮产生。总之，AVP和Ang II不同的类固醇生成作用似乎源于在持续的促分泌素刺激过程中引发的明显不同的Cai反应。
