We recently reported evidence for impairment of endothelium-dependent relaxation (EDR) and decreased agonist-stimulated endothelial synthesis/release of nitric oxide (NO) using in vitro aortic and coronary preparations isolated from endotoxemic guinea pigs. We tested the hypothesis that impaired EUR involves dysfunctional endothelial Ca i regulation by using fura-2 microfluorometry to compare agonist-stimulated Ca i responses of endothelial cells (EC) 16 h after intmperiloneal injection of bacterial endotoxin (LPS; 4 mg/kg] or saline (CON). Basal Ca i (340/380 nm fluorescence ratio. R) was not different in CON and LPS EC (1.1±.03 and 1.1±03 respectively). Exposure of EC to ADP (10 μM), in the presence of extracellular Ca 2+ (2mM) produced hiphasic increases in Ca i that were markedly decreased (P<0.05) in EC from LPS-treated animals. Peak ADP-stimulated Ca, responses (R) averaged 2.2 ± .21 in CON EC and 1.5 ±.11 in EC from LPS-treated animals. Exposure of the same EC to acetylcholine (ACh; 10 μM) produced sustained increases in Ca (R=1.4±13) in CON EC; however, LPS abolished Ca i responses to ACh. Moreover. ACh (but not ADP) Ca i responses rapidly decreased with time (within 2 h) after dispersion. In conclusion, our data demonstrate impaired agonist -stimulated endothelial Ca i mobilization; the dependence of NO synthesis on Ca i suggests that Ca, defects may contribute to LPS-induced impaired EDR.
|Original language||English (US)|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology