Comparison of microvascular pressures in normal and spontaneously hypertensive rats

Abstract

The principal cardiovascular manifestations of essential hypertension are known to be an increase in peripheral vascular resistance and in systemic arterial blood pressure. However, it is not known if the increased vascular resistance is of appropriate location and magnitude to prevent an elevation of pressures in the microvasculature during hypertension. To examine this possibility, the pressures and diameters of microvessels in the cremasteric muscle were measured in normal (NR) and spontaneously hypertensive rats (SHR). The pressures and diameters in comparable orders of vessels in NR and SHR at their respective systemic arterial pressures of 88.5 ± 2.1 and 115.6 ± 1.8 mm Hg at age 7–8 weeks were measured by the servonull micropipet technique. Both the systemic pressure and the microvascular pressure in SHR are 30–35% higher than those measured in NR. The diameters of the arterioles and venules in SHR are as large or larger than comparable orders of vessels in NR. Therefore, the reported increase in vascular resistance during hypertension seems not to be caused by vasoconstriction of vessels in SHR as compared to NR, nor does the increased resistance prevent an increase in microvascular pressures.