Myogenic responses of isolated rat skeletal muscle venules; its
characteristics and modulation by norepinephrine and endothelium.
D[diaeresis]ornyei, Gabriella, Emil Monos, Gabor Kaley, and Akos
Koller.
Clinical Research Department - 2nd Institute of Physiology,
Semmelweis University of Medicine, Budapest, Hungary and Department
of Physiology, New York Medical College, Valhalla, NY
APStracts 2:0548H, 1995.
The pressure-induced myogenic response of large venules of skeletal
muscle and its possible interactions with adrenergic receptor
activation and endothelial factors have not yet been elucidated.
Therefore, first order venules of rat gracilis muscle were isolated,
cannulated and placed in an organ chamber. Changes in internal
diameter of the vessels as a function of perfusion pressure (PP) were
obtained. In response to increases in PP (0.5 -17.5 mmHg), the
diameter of venules increased from 197.1+/-23.96[mu]m to 369+/
-14.1[mu]m. In passive conditions (in Ca2+-free solution), the
pressure-diameter curve of venules shifted significantly upward. In
the presence of norepinephrine (NE, 10-6M) in the bath solution the
pressure-diameter curve of active venules shifted significantly
downward and in the pressure-normalized diameter curve, a negative
slope developed (-6.1+/-4.6). Both in the absence and presence of NE,
removal of endothelium significantly reduced venular diameters in the
pressure range of 3-5 and 2-5 mmHg respectively, but did not change
significantly the characteristics of the pressure-diameter curves.
These findings indicate, that the smooth muscle of venules actively
responds to changes in intraluminal pressure. This response is
greatly facilitated by NE and modulated by the endothelium. The
myogenic response of skeletal muscle venules, especially in the
presence of norepinephrine, could have a role in the regulation of
the resistance and capacitance of venules, and consequently blood
flow and tissue exchange in skeletal muscle.
Received 29 September 1995; accepted in final form 28 November
1995.
APS Manuscript Number H917-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95