The erythrocyte as a regulator of vascular tone .
Ellsworth, Mary L., Thomas Forrester, Christopher G. Ellis, and Hans
H. Dietrich.
Department of Pharmacological and Physiological Science, Saint
Louis University School of Medicine, St. Louis, MO 63104, USA,
Department of Medical Biophysics, University of Western Ontario,
London, Ontario, N6A 5C1, Canada, Department of Neurosurgery,
Washington University School of Medicine, St. Louis, MO 63106,
USA
APStracts 2:0410H, 1995.
Local regulation of microvascular blood flow is a complex process in
which the needs of the tissue must be communicated to the vasculature
enabling the appropriate matching of oxygen (O2) supply to demand. We
hypothesize that the red blood cell (RBC) is not only the major O2
carrier but also serves as an O2 sensor and affector of changes in O2
delivery via its release of ATP which subsequently binds to P2y
receptors on the vascular endothelium altering vessel calibre. Using
the hamster as a model, we determined that the efflux of ATP from
RBCs following exposure to low PO2 (PO2 = 17 +/- 6 mmHg) and low pH
(pH = 7.06 +/- 0.07) solutions was significantly (p<0.01)
greater than following exposure to normoxic, normal pH (PO2 = 87 +/-
4; pH = 7.38 +/- 0.04) solutions indicating that two factors which
are associated with an impaired O2 supply relative to demand,
increase the release of ATP from the RBC. To ascertain if ATP alters
vascular calibre, we applied 10-6 M ATP intraluminally to arterioles
of the retractor muscle using a micropressure system. Vessel diameter
increased 8 and 10%, 140 +/- 60 [mu]m upstream of the site of
infusion following 50 and 500 msec pulses, respectively. Application
of ATP to arteriolar and venular capillaries induced a 31 and 81%
increase in RBC supply rate, respectively. These results support our
hypothesis that the RBC is more than just an O2 carrier having a
direct role in the regulation of vascular tone.
Received 11 May 1995; accepted in final form 7 September 1995.
APS Manuscript Number H453-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.