AJP - Cell Physiology, Vol 259, Issue 4 C675-C686, Copyright © 1990 by American Physiological Society
Spatial dynamics of intracellular calcium in agonist-stimulated vascular smooth muscle cells
C. B. Neylon, J. Hoyland, W. T. Mason and R. F. Irvine
Department of Biochemistry, AFRC Institute of Animal Physiology and Genetics Research, Cambridge, United Kingdom.
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.
