DIRECT IN-VIVO MEASUREMENT OF GASTRIC MICROVASCULAR PRESSURES IN THE RAT

There are no direct data available on micropressures in the gastric mi crocirculation in spite of its pivotal role in the development of acut e gastric mucosal lesions. Our goal was to develop an in vivo method t o directly measure intravascular pressure and vessel diameter in vario us gastric microvessels. This paper describes methods and procedural d etails of our novel preparation of the exteriorized rat stomach for va scular 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 seromuscul ar preparation to study the circulation of superficial outer muscular layers and a submucosal preparation-following careful dissection of th e seromuscular layer-to study the submucosal and deeper mucosal microc irculations. Intravascular hydrostatic pressure was measured with a se rvo-null micropressure measuring system, while vessel diameter was eva luated on the television screen with videometry. Data (average +/- SE) were obtained from muscular arterioles (20.8 +/- 0.93 mu m; 29.8 +/- 1.32 mmHg), venules (23.4 +/- 1.61 mu m; 18.1 +/- 0.61 mmHg), submucos al arterioles (50.9 +/- 3.55 mu m; 55.4 +/- 2.78 mmHg), venules (53.7 +/- 2.06 mu m; 21.4 +/- 0.73 mmHg), and deeper mucosal arterioles (20. 2 +/- 1.06 mu m; 33.8 +/- 0.81 mmHg), venules (29.9 +/- 1.17 mu m; 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 ap plicability of this method to examine the effects of systemic blood pr essure reduction and local application of vasoactive agents on the gas tric microcirculation. This method is useful for analyzing the microci rculation of the stomach in vivo under different experimental conditio ns. (C) 1998 Academic Press.