Cytosolic Calcium and Aldosterone Response Patterns of Rat Adrenal Glomerulosa Cells Stimulated by Vasopressin: Comparison with Angiotensin II*

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 Ca; rise showed little dependency on AVP or Ang II concentration. At most AVP concentrations, the response consisted of Ca; oscillations, with apparent fusion of these Caj oscillations at the highest AVP concentrations (1–0.1 μM). Similar oscill...