Static Mechanical Characteristics of the Small Collecting Vein and the First-Order Venule in the Denervated Small Intestines of the Wistar, Wistar-Kyoto, and Spontaneously Hypertensive Rats

193 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1983.This study was centered around two basic themes. The first related to the mechanics of the venous system, the second to venous function in hypertension. Since the venous system holds a large fraction of the total peripheral blood volume (and much of this possibly located in the venous microcirculation), and understanding of venule distention characteristics is important. In addition, veins in hypertensive animals appear to be stiffer than their controls; thus microvascular assessment of the hypertensive venous system is needed. The two hypotheses of this project were that (1) wall structure of a venule is a significant factor in determining distension characteristics during venous pressure elevation, and (2) venule wall stiffness is significantly increased in the spontaneously hypertensive rat (SHR).To test these hypotheses, distension parameters (compliance, distensibility, and strain) and wall stiffness (incremental elastic modulus) were calculated from the distension curves of the small collecting vein (SCV) and the first-order venule (1V) within the denervated small intestines of the Wistar, Wistar-Kyoto, and spontaneously hypertensive rats. The data indicate that the SCV was stiffer than the 1V, even though it underwent equal or larger volume changes. Although much of this difference in stiffness was due to the different wall stress levels, a significant difference in stiffness was found between the SCV and 1V, which remained after taking into account the possible stiffening effect of the interstitial matrix. Thus some factor other than wall stress and the interstitium caused the SCV-1V difference, possibly wall structure. These results do not disprove our first hypothesis. The data contradict the second hypothesis for the conditions of our experiment, since the SHR only had stiffer 1V, and the margin of difference between this and the Wistar-Kyoto 1V was small. We would therefore reject this hypothesis for the pressure ranges measured in the denervated small intestine.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD