AJP - Heart and Circulatory Physiology, Vol 256, Issue 1 47-H55, Copyright © 1989 by American Physiological Society
Electrical and mechanical responses of rat saphenous vein to short-term pressure load
E. Monos, S. J. Contney, A. W. Cowley Jr and W. J. Stekiel
Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
The magnitude and mechanism of myogenic response of vascular smooth muscle
(SM) in rat distal saphenous vein was assessed from SM membrane potential
(Em) measured in situ and in vitro with glass microelectrodes and from
active and passive stress and strain calculated from changes in vessel
diameter measured in vitro via videomicroscopy. Elevation of intraluminal
pressure from 2.2 +/- 0.2 (SE) mmHg (control) to 15 +/- 0.8 mmHg for 1 h in
a series of in vitro vessel segments perfused with physiological salt
solution at 0.2 ml/min induced a maintained and reversible depolarization
of 18 +/- 0.9 mV. A 7.6 +/- 0.4-mmHg pressure increase induced a 12.9 +/-
1.2-mV depolarization in a second series. In a third series, 5-mmHg
pressure increments induced significant increments in active isometric
stress and isobaric strain. Opening an acute, reversible in situ femoral
artery to saphenous vein shunt caused a 4- to 5-mmHg venous pressure
elevation, a 10-fold increase in venous blood flow, and a 12.1 +/- 0.9-mV
venous SM depolarization. Thus a short-term pressure load causes sustained,
reversible venous SM cell depolarization both in vitro and in situ, coupled
with active strain and stress generation in the vein wall. These results
support our hypothesis that SM of peripheral veins can contribute to an
intrinsic capacity autoregulation.
