Nitric oxide induces transient Ca2+ changes in endothelial cells independent of cGMP

✍ Scribed by Thomas Volk; Karsten Mäding; Mario Hensel; Wolfgang J. Kox

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 301 KB
• Volume: 172
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/(sici)1097-4652(199709)172:3<296::aid-jcp3>3.0.co;2-j

✦ Synopsis

Ca 2/ changes induced by nitric oxide (NO • ) were investigated in cultured human endothelial cells. Sodium nitroprusside (SNP) (1-100 mmol/L) and S-Nitroso-Nacetylpenicillamine (SNAP) (100 mmol/L) were used as NO • donors. The cytoplasmatic Ca 2/ concentration was calculated using ratiometric FURA2 fluorescence measurements. Both NO • donors caused transient oscillatory Ca 2/ changes, which were not detectable in the presence of oxyhemoglobin (50 mmol/ L). Digital ratio imaging revealed initiation sites within cells where Ca 2/ increases started spreading, which indicates that nonuniformly distributed targets might be involved in these reactions. Calcium was released from intracellular stores as indicated by experiments performed in Ca 2/ -free buffer. L-type Ca 2/ -channel blocker diltiazem (100 mmol/L) was not able to block these responses. NO •induced Ca 2/ release from intracellular stores caused capacitative Ca 2/ entry. Both thapsigargin (1 mmol/L) and cyclopiazonic acid (10 mmol/L) inhibited the SNP response completely, whereas neither ryanodine (up to 100 mmol/L) nor dantrolene (100 mmol/L) was able to inhibit Ca 2/ changes induced by SNP, indicating that primarily inositol 1,4,5-triphosphate (IP 3 )-dependent stores are released upon stimulation with NO • . A small inhibitory effect of ATP-and SNPinduced peak [Ca 2/ ] i increase was measured in the presence of both caffeine (20 mmol/L) and procaine (1 mmol/L). Evidence is presented that cGMP is not involved in NO • -induced Ca 2/ signals, as neither inhibitors of guanylate cyclase (methylene blue and LY 83583) nor cell permeant analogues of cGMP altered or simulated [Ca 2/ ] i changes. An inhibitor of cGMP-dependent protein kinase was also ineffective. We therefore propose that endothelial cells have specific targets proximal or at IP 3 receptors to induce Ca 2/ changes in endothelial cells stimulated with NO • .