AJP - Gastrointestinal and Liver Physiology, Vol 257, Issue 4 633-G636, Copyright © 1989 by American Physiological Society
Gastric oxygen uptake during autoregulatory escape from sympathetic stimulation
J. W. Kiel and A. P. Shepherd
Department of Physiology, University of Texas Health Science Center, San Antonio 78284.
To assess the effects of sympathetic stimulation on gastric blood flow and
oxygen utilization, the perivascular nerves were stimulated at 2, 4, 6, and
8 Hz in chambered segments of canine gastric corpus perfused at constant
pressure. Spectrophotometric arteriovenous oxygen difference and
electromagnetic blood flow were recorded continuously. Except at the lowest
frequency of stimulation (2 Hz), total blood flow exhibited autoregulatory
escape, i.e., blood flow decreased initially but then returned toward
control. The fall in total blood flow at the onset of sympathetic
stimulation was smaller at 2 Hz than at 4 Hz, but stimulation at 6 and 8 Hz
caused no further reductions in total blood flow. However, at all
frequencies, total blood flow escaped to the same steady-state value
(approximately 17 ml.min-1.100 g-1). Although total blood flow was still
less than control (approximately 25 ml.min-1.100 g-1), oxygen extraction
increased proportionately so that oxygen consumption was not significantly
less than control at any frequency of stimulation. We conclude that
autoregulatory escape from sympathetic stimulation is mediated by local
mechanisms acting to maintain tissue oxygenation in the stomach.
