Direct pressure and diameter measurements were recorded in the innervated and denervated microcirculation of rat intestinal muscle at control (100-110 mm Hg) and reduced systemic arterial pressures. The measurements were made with a servo-null pressure transducer and video micrometer system. The goals of the study were (1) to determine if significant differences exist between the pressure distributions in innervated and denervated intestinal muscle microvessels at normal and reduced systemic pressures; (2) to see if neural and local vascular mechanisms influence capillary pressures and microvascular pressure distributions in intestinal muscle; and (3) to ascertain the relative contribution of individual microvascular segments to the pressure distribution within the intestinal microcirculation. The results indicate that there is a simple, linear relationship between microvascular pressures and systemic pressure, with no significant difference (P > 0.05) between the results from innervated and denervated tissues, except for second-order venules. Denervation did not alter the pressure distribution within the microcirculation. However, denervation did cause a significant dilation (P < 0.05) of the small arterioles and a very large increase in the diameter of venous microvessels. Thus, the major effect of denervation was to cause a decrease in the postcapillary to precapillary resistance ratio and an increase in flow through the intestinal muscle without any significant or measurable change in the microvascular pressure distribution. Furthermore, capillary pressures in both innervated and denervated tissues were not significantly different (P > 0.05) at normal or reduced systemic pressures, but changed in direct linear proportion to changes in systemic arterial pressure. This result is in direct opposition to the idea of an "autoregulatory" mechanism for local control of capillary hydrostatic pressure, but is consistent with the concepts of local blood flow regulation.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Cell Biology