AJP - Heart and Circulatory Physiology, Vol 249, Issue 3 470-H476, Copyright © 1985 by American Physiological Society
Measurement of calcium influx in tethered rings of rabbit aorta under tension
M. M. Gleason, P. H. Ratz and S. F. Flaim
Calcium (Ca) influx in vascular smooth muscle is routinely measured in
untethered preparations not under passive stretch, and Ca influx data are
correlated with data for steady-state isometric tension obtained under
parallel conditions from tethered preparations under passive stretch. The
validity of this method was tested by simultaneous measurement of Ca influx
and tension in tethered rings of rabbit thoracic aorta. Ca influx (45Ca
3-min pulse) and tension were measured at 3 and 30 min after norepinephrine
(NE) or KCl and under control (no agonist) conditions. Active tension was
significantly altered by variations in passive tension. Ca influx was
unaffected by passive tension under control, NE, or KCl conditions, and
results were similar at 3 and 30 min. The results confirm the validity of
correlating Ca influx data from untethered rings with steady-state
contractile response data obtained from tethered rings under similar
experimental conditions.
