Spatial dynamics of intracellular calcium in agonist-stimulated vascular smooth muscle cells.
Vasoconstrictor agonists stimulate smooth muscle contraction by inducing a rise in intracellular free Ca2+. Digital-imaging microscopy of fura-2 fluorescence from single vascular smooth muscle cells cultured from the human internal mammary artery has allowed us to record the subcellular alterations in Ca2+ that occur immediately after stimulation by receptor agonists. The thrombin-induced rise in cytoplasmic free Ca2+ begins in a discrete region typically located close to the end of the cell. Subsequently, this region of elevated Ca2+ expands until Ca2+ is elevated throughout the cell cytoplasm. The rate of spreading in the region of elevated Ca2+ in a linear direction averaged 10.1 microns/s, enabling it to traverse the length of most cells within approximately 5 s, and involved rises in Ca2+ of between 200 and 500 nM. In some cells, the Ca2+ rise began at both ends and collided midway. Similar dynamic changes in the spatial distribution of Ca2+ were recorded in cells stimulated by acetylcholine. The novel observation that vasoconstrictor agonists induce an elevation of Ca2+ in a localized region which subsequently expands throughout the cytoplasm of single smooth muscle cells may provide new insight into the nature of Ca2+ signaling in vascular tissue.
Neylon
C B
CB
Department of Biochemistry, AFRC Institute of Animal Physiology and Genetics Research, Cambridge, United Kingdom.
Hoyland
J
J
Mason
W T
WT
Irvine
R F
RF
D000109:Acetylcholine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004594:Electrophysiology / Q000379:methods; D016257:Fura-2; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology*; D007700:Kinetics; D008323:Mammary Arteries / Q000187:drug effects / Q000502:physiology; D008856:Microscopy, Fluorescence; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D013347:Subcellular Fractions / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology*; D013997:Time Factors; D014741:Video Recording
D015759:Ionomycin; D013917:Thrombin; D000109:Acetylcholine; D002118:Calcium; D016257:Fura-2