title: Cytosolic calcium concentration in resting and stimulated endothelium of excised intact rat aorta.
abstract: 1. Optical fibres were used to excite and record fluorescence from the lumenal face of rat aorta or tail artery loaded with fura-2. 2. Acetylcholine (ACh) evoked an endothelium-dependent rise in the fura-2 340/380 nm excitation ratio in both vessels. High [K+] or phenylephrine evoked an endothelium-independent rise in ratio in tail artery but failed to increase the ratio in aorta. These observations indicate that fura-2 fluorescence and therefore cytosolic calcium concentration ([Ca2+]i) may be selectively recorded from the endothelium of intact rat aorta. 3. In aortic endothelium, resting [Ca2+]i was 95 +/- 8 nM (n = 44). ACh evoked a monophasic rise in [Ca2+]i which was temporally coincident with a membrane hyperpolarization. 4. ATP in most (22/35) preparations evoked a rise in [Ca2+]i which declined towards resting and was followed by a secondary rise. The biphasic [Ca2+]i responses were accompanied by biphasic electrical responses of initial hyperpolarization followed by depolarization above the resting potential and subsequent restoration towards rest. In the presence of high [K+] or the K+ ionophore valinomycin, ATP did not evoke changes in membrane potential and only monophasic rises in [Ca2+]i were observed. In some (7/35) preparations, ATP evoked oscillations in [Ca2+]i, with membrane potential oscillating in antiphase. 5. These data suggest interplay between [Ca2+]i and membrane potential in the generation of agonist-evoked responses in native endothelium in situ. The observed oscillations in [Ca2+]i imply spatio-temporal synchronization of Ca2+ signalling in large groups of endothelial cells in intact rat aorta.
authors.affiliation: Physiological Laboratory, University of Cambridge, UK.
authors.forename: Y M
authors.initials: YM
authors.lastname: Usachev
authors.forename: S M
authors.initials: SM
authors.lastname: Marchenko
authors.forename: S O
authors.initials: SO
authors.lastname: Sage
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000378:metabolism / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D004727:Endothelium / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013997:Time Factors
chemical_list: D000255:Adenosine Triphosphate; D000109:Acetylcholine; D002118:Calcium