Direct in vivo measurement of gastric microvascular pressures in the rat

There are no direct data available on micropressures in the gastric microcirculation in spite of its pivotal role in the development of acute gastric mucosal lesions. Our goal was to develop an in vivo method to directly measure intravascular pressure and vessel diameter in various gastric microvessels. This paper describes methods and procedural details of our novel preparation of the exteriorized rat stomach for vascular micropuncture studies. The stomach of the anesthetized rat was fixed with minimal surgery in a temperature-controlled gastric chamber. Two preparations were used, both from the serosal side: a seromuscular preparation to study the circulation of superficial outer muscular layers and a submucosal preparation-following careful dissection of the seromuscular layer-to study the submucosal and deeper mucosal microcirculations. Intravascular hydrostatic pressure was measured with a servo-null micropressure measuring system, while vessel diameter was evaluated on the television screen with videometry. Data (average +/- SE) were obtained from muscular arterioles (20.8 +/- 0.93 micron; 29.8 +/- 1. 32 mmHg), venules (23.4 +/- 1.61 micron; 18.1 +/- 0.61 mmHg), submucosal arterioles (50.9 +/- 3.55 micron; 55.4 +/- 2.78 mmHg), venules (53.7 +/- 2.06 micron; 21.4 +/- 0.73 mmHg), and deeper mucosal arterioles (20.2 +/- 1.06 micron; 33.8 +/- 0.81 mmHg), venules (29.9 +/- 1.17 micron; 25.8 +/- 0.47 mmHg), at a systemic arterial pressure of 110 +/- 2.4 mmHg (n = 10 each from 14 animals). Further experiments demonstrated the applicability of this method to examine the effects of systemic blood pressure reduction and local application of vasoactive agents on the gastric microcirculation. This method is useful for analyzing the microcirculation of the stomach in vivo under different experimental conditions.