Heterogeneity of [Ca(2+)](i) signaling in intact rat aortic endothelium.
Most existing knowledge about [Ca(2+)](i) signaling in vascular endothelium has been based on studies using endothelial cells cultured in vitro. To examine how endothelial cells behave in situ, we have developed a method to monitor single-cell [Ca(2+)](i) from Fura-2-loaded rat aortic segments. Fluorescence ratio images from large numbers of endothelial cells were acquired by using a flow chamber mounted on a dual-wavelength fluorescence microscope. Our results showed that either acetylcholine or histamine reversibly activated the vascular endothelium by eliciting M(3) or H(1) receptor-mediated [Ca(2+)](i) increases, respectively. The acetylcholine-evoked endothelial [Ca(2+)](i) elevation at the branch site (intercostal orifice) was much more pronounced than that at the non-branch area. However, endothelium at the branch site was relatively insensitive to histamine. Both acetylcholine-sensitive and histamine-sensitive endothelial cells were arranged in belts aligned along flow lines and were intercalated with each other. Data analyzed from 400 endothelial cells located at the non-branch site showed drastically heterogeneous [Ca(2+)](i) responses to a fixed concentration of either acetylcholine or histamine, differing by two orders of magnitude in individual cells. As a conclusion, vascular endothelial cells appear to have their own characteristic [Ca(2+)](i) 'fingerprint' to various agonists and they may function coordinately in situ.
Huang
T Y
TY
Department of Physiology, National Cheng-Kung University Medical College, Tainan 701, Taiwan.
Chu
T F
TF
Chen
H I
HI
Jen
C J
CJ
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D005456:Fluorescent Dyes; D016257:Fura-2; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D017208:Rats, Wistar
D005456:Fluorescent Dyes; D006632:Histamine; D000109:Acetylcholine; D016257:Fura-2