Angiotensin II-activated Ca2+ entry-induced release of Ca2+ from intracellular stores in rat portal vein myocytes

Br J Pharmacol. 1996 May;118(1):73-8. doi: 10.1111/j.1476-5381.1996.tb15368.x.


1. The action of angiotensin II (AII) was studied in single myocytes from rat portal vein in which the cytoplasmic Ca2+ concentration was estimated by emission from dyes Fura-2 or Indo-1 and the Ca2+ channel current was measured with the whole-cell mode of the patch-clamp technique. 2. Most of the AII-evoked increases in [Ca2+]i were reduced by about 60% after pretreatment with ryanodine and caffeine to deplete intracellular Ca2+ stores. However, in some cells the AII-induced Ca2+ responses were of small amplitude and resembled those obtained in the presence of ryanodine and caffeine. Both types of Ca2+ responses induced by AII were selectively inhibited by losartan, suggesting that the AII effects resulted from activation of the angiotensin AT1 receptors. 3. The concentration-response curve to AII had an EC50 value close to 1 nM for the increase in [Ca2+]i obtained after depletion of intracellular Ca2+ stores. This value was increased to around 18 nM in experiments where the intracellular Ca2+ stores were not depleted. 4. AII-evoked Ca2+ responses were abolished in the absence of external Ca2+ and in the presence of 1 microM oxodipine to block L-type Ca2+ channels. 5. Intracellular applications of the InsP3 receptor antagonist, heparin or an anti-PdtIns antibody did not modify AII-induced Ca2+ responses. 6. Our results show that AII releases Ca2+ from intracellular stores without involving InsP3 but through a Ca2+ release mechanism activated by Ca2+ influx through L-type Ca2+ channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiotensin II / antagonists & inhibitors
  • Angiotensin II / pharmacology*
  • Animals
  • Antibodies / pharmacology
  • Calcium / metabolism*
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / drug effects
  • Calcium Channels / metabolism
  • Calcium Channels / physiology
  • Cells, Cultured
  • Cytosol / metabolism
  • Heparin / pharmacology
  • Inositol 1,4,5-Trisphosphate Receptors
  • Membrane Potentials / drug effects
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / drug effects*
  • Muscle, Smooth, Vascular / metabolism*
  • Phosphatidylinositols / immunology
  • Portal Vein / cytology
  • Rats
  • Rats, Wistar
  • Receptors, Cytoplasmic and Nuclear / physiology


  • Antibodies
  • Calcium Channel Blockers
  • Calcium Channels
  • Inositol 1,4,5-Trisphosphate Receptors
  • Phosphatidylinositols
  • Receptors, Cytoplasmic and Nuclear
  • Angiotensin II
  • Heparin
  • Calcium