[Study on Servo-null method for direct measurement of microvascular pressure by micropuncture technique]

The dynamic microvascular pressures in the mesentery of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were measured and recorded by using the Servo-null microvascular pressure measuring system (Model 4A, IPM, Inc., San Diego, USA) with glass micropipettes whose tips were 1.0-5.0 microns in diameter and had been beveled very sharply at an angle of 25 degree. Microvascular pressures were measured in two groups of microvessels: large, 25-45 microns; small, 15-25 microns. Mean microvascular pressures (Pm) of large and small arterial microvessels in SHR were 6.0 +/- 7.0 kPa and 4.8 +/- 0.6 kPa, respectively. In WKY rats, Pm were 4.2 +/- 0.6 kPa and 3.6 +/- 0.6 kPa, respectively. Pm of comparable types of arterial microvessels in SHR and WKY rats was significantly different. No significant difference of Pm in small venous vessels was found between SHR and WKY rats.