Autoregulation of gastric blood flow and oxygen uptake

Abstract

The purpose of this study was to determine whether the ability of the stomach to autoregulate blood flow and oxygen uptake is altered by sympathetic denervation. Blood flow, oxygen extraction, local arterial pressure, and venous pressure were continuously monitored in sympathetically innervated and denervated autoperfused dog stomach preparations. As perfusion pressure was reduced in increments from 120 to 20 mmHg in innervated preparations, blood flow and oxygen uptake decreased while oxygen extraction and vascular resistance increased. Reductions in perfusion pressure in denervated preparations resulted in a decrease in blood flow, oxygen uptake, and vascular resistance, whereas oxygen extraction increased. The ability of the stomach to regulate blood flow and oxygen uptake was significantly improved after denervation, i.e., vascular resistance decreased and oxygen uptake remained relatively constant when arterial pressure was reduced. Oxygen uptake in denervated stomachs was generally higher than that in innervated stomachs. Autoregulation of gastric blood flow therefore appears to be improved by denervation. The better autoregulation observed after denervation may result either from a reduction in sympathetic tone and/or the increase in gastric oxygen demand.

Autoregulation of blood flow.

“…This was shown in skeletal muscle by Stainsby,8 in stomach by Holm-Rutili et al 9 and in intestine by Norris et al 10 The key factor in the enhancement of autoregulation may be a lowering of tissue oxygen levels as oxygen consumption increases." Venous O 2 levels in resting skeletal muscle are relatively high (70% saturated), reflecting a high tissue PO 2 .…”

“…The net result in skeletal muscle arterioles is constriction in larger arterioles and dilation of the more distal arterioles." 9 The latter can be prevented in thin muscle by elevating the O1 2 02 level over the muscle surface. Sympathetic nerve stimulation does not inhibit autoregulation in the brain but does alter the autoregulatory range.…”

Effects of vesical and perfusion pressure on perfusate flow, and flow on vesical pressure, in the isolated perfused working pig bladder reveal a potential mechanism for the regulation of detrusor compliance

“…For example, the renal circulation maintains a constant blood flow over a pressure range of 75‐180 mmHg . Splanchnic circulatory beds such as gastric and colonic circulations generally lack an autoregulatory mechanism. Instead, O 2 extraction increases when blood pressure declines.…”

The adrenal medulla protects against stress ulcers in the presence of gastric sympathectomy

“…Besides stable acid secretion and enhanced aminopyrine clearance after S-SX other mechanisms may account for the decrease in ulcer index: (1) oxygen extraction by gastric tissue is elevated following sympathectomy [5] and (2) glucose and insulin metabolism may be altered in that way leading to improved intracellular energy supply (i.e., glucose) [11]. Although we can only document static values for glucose and insulin, it is well-known that insulin and glucose kinetics are deeply influenced by the sympathoadrenal system [10].…”