Endothelial [Ca2+]iis an integrating signal for the vascular tone in rat aortae
✍ Scribed by Tung-Yi Huang; Hsiun-ing Chen; Chin-Yen Liu; Chauying J Jen
- Book ID
- 104497839
- Publisher
- BioMed Central
- Year
- 2001
- Tongue
- English
- Weight
- 626 KB
- Volume
- 1
- Category
- Article
- ISSN
- 1472-6793
No coin nor oath required. For personal study only.
✦ Synopsis
Background: Although various endothelium-dependent relaxing factors (endothelial autacoids) are released upon the elevation of endothelial cytosolic free Ca 2+ concentration (EC [Ca 2+ ] i ), the quantitative relationship between EC [Ca 2+ ] i and vascular tone remains to be established. Moreover, whether the basal release of endothelial autacoids is modulated by basal EC [Ca 2+ ] i is still unclear. We assessed these issues by using a novel method that allows simultaneous recording of EC [Ca 2+ ] i and vascular displacement in dissected rat aortic segments.
Results:
Receptor-dependent (acetylcholine) or independent (ionomycin) agonists caused immediate EC [Ca 2+ ] i elevation followed by vasorelaxation in preparations pre-contracted with phenylephrine. Low doses of agonists induced small EC [Ca 2+ ] i elevations (about 100 nmol/L) and concomitant half-maximal vasorelaxation. At high doses, agonists elevated EC [Ca 2+ ] i to µmol/L range with little additional vasodilatation. When EC [Ca 2+ ] i was plotted against the vasorelaxation, the curves were almost identical for both acetylcholine and ionomycin treatments, in the presence or absence of various endothelial autacoid inhibitors. Calcium-free solution reduced basal EC [Ca 2+ ] i and induced a drastic vasoconstriction. Endothelial autacoid inhibitors reduced EC [Ca 2+ ] i changes and abolished both agonist-induced vasodilatation and calcium-free solution-induced vessel contraction. When the EC [Ca 2+ ] i was completely chelated by 40 µmol/L BAPTA, the acetylcholine-evoked vasorelaxation could be abolished as well. However, when the EC [Ca 2+ ] i was partially chelated by 20 µmol/L BAPTA, the acetylcholine-evoked vasorelaxation was almost unaffected.
Conclusions:
These results indicate that vascular tone is modulated by subtle changes of EC [Ca 2+ ] i level, which seems to serve as an integrating signal in both basal and stimulated states.