Autoregulation of canine gastric mucosal blood flow

Although autoregulation of total blood flow has been demonstrated in the stomach, autoregulation of gastric mucosal blood flow has not been investigated due to the limitations of previously available mucosal blood flow measuring techniques. We recently evaluated laser-Doppler velocimetry for use in the stomach and found it to yield continuous, superficial measurements of either mucosal or muscularis blood flow. In the present study, simultaneous measurements of total, mucosal, and muscularis blood flows and arteriovenous oxygen difference were made during step decreases in perfusion pressure in chambered segments of resting canine stomach. As perfusion pressure was decreased from 180 to 35 mmHg, oxygen consumption remained relatively constant at 1.5 ml/min X 100 g and only became blood flow-dependent when perfusion pressure was set below 90 mmHg and total blood flow fell below 35 ml/min X 100 g. Oxygen consumption was maintained partly by increased oxygen extraction; however, there was also a progressive increase in the tendency for total blood flow autoregulation after each drop in perfusion pressure. Mucosal blood flow was also well autoregulated over the physiologic range of perfusion pressure and remained relatively constant during the plateau portion of the oxygen consumption curve. Our results indicate that in the resting stomach, oxygen consumption is maintained by changes in oxygen extraction in conjunction with autoregulation of mucosal and total blood flow.