Resting oxygenation of rat and rabbit intestine: arteriolar and
capillary contributions.
Bohlen, H. Glenn, Julia M. Lash.
Department of Physiology and Biophysics, Indiana University Medical
School, 635 Barnhill Drive, Indianapolis, IN 46202
APStracts 2:0161H, 1995.
Counter-current exchange of oxygen may occur between inflow and
outflow microvessels of the small intestine and greatly influence the
dominant sites of tissue oxygenation. To determine the location and
magnitude of potential exchange, percent saturation of hemoglobin
with oxygen (%SHb) was measured in microvessels throughout the
intestine of rats and rabbits. Oxygen losses from systemic arterial
blood through large and intermediate arterioles (2A) was 5-7 %SHb in
both species and there was no evidence of an increase in %SHb along
intermediate and large venules. A larger loss of oxygen from
arterioles and an increase in venous saturation would be evident if
significant arteriolar to venular counter-current exchange of oxygen
occurred in the submucosa. From 2A to the villus tip, arteriolar %SHb
decreased 10% SHb in rabbits and 15% SHb in rats; the villus tip %SHb
was 72.9+3.9 %SHb in rabbits and 69.9+2.9 %SHb in rats. An additional
decrease of 5 %SHb in rabbits and 15 %SHb in rats occurred across the
villus capillaries and smallest venules. Although the total reduction
in %SHb across the villi was different between the two species, 70
-90% of the total AV oxygen losses occurred in the capillaries and
small arterioles of the villi. We found no evidence of counter
-current exchange of oxygen in villi or any other vascular region.
Rather, as appears to occur in most organs, small arterioles in
conjunction with capillaries dominate resting oxygen exchange to
tissue.
Received 5 January 1995; accepted in final form 13 April 1995.
APS Manuscript Number H5-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 2 May 1995.