AJP - Heart and Circulatory Physiology, Vol 253, Issue 6 1456-H1461, Copyright © 1987 by American Physiological Society
Ca2+ signals obtained with multiple indicators in mammalian vascular muscle cells
T. T. DeFeo, G. M. Briggs and K. G. Morgan
Cardiovascular Division, Charles A. Dana Research Institute, Boston, Massachusetts.
Enzymatically isolated single cells from ferret portal vein were loaded
with the fluorescent dyes fura-2 and chlortetracycline. Ferret portal vein
intact strips were loaded with the luminescent indicator aequorin. At short
loading times, fura-2 loading resulted in relatively homogeneous images of
labeled cells. At longer loading times, extremely heterogeneous images were
obtained that were similar to those produced by chlortetracycline, an
indicator recognized to enter calcium-storage organelles. A significant
effect of fura-2 on contractile function was detected at the long but not
at the short loading time. Caffeine, which is known to deplete calcium from
sarcoplasmic reticulum, decreased the fura-2 fluorescent intensity when
cells were incubated for a long loading time but caused no statistically
significant change at the short loading time. Caffeine caused no drop in
the aequorin signal but did cause a drop in the chlortetracycline
fluorescence. These results are consistent with the idea that aequorin
reports cytoplasmic intracellular calcium concentration ([Ca2+]i),
chlortetracycline reports stored calcium, and fura-2 reports a mixed signal
from the cytoplasm and calcium-storage organelles depending on incubation
time.
