Comparison of the Microvascular Network Resistance between Normotensive and Spontaneously Hypertensive Rats

Abstract

Elevated blood pressure during hypertension has been associated with microvascular rarefaction defined by a loss of arterioles, capillaries and/or venules. Recent work in our laboratory suggests that rarefaction is more complex and is accompanied by network patterning alterations. However, the influences of these alterations on network resistance remain unclear. The object of this study was to compare microvascular network resistances across spontaneous hypertensive and normotensive rat strains over the time course of blood pressure elevation. Mesenteric tissues from age‐matched (4/7‐8/15‐16 weeks) male spontaneously hypertensive (SHR; n = 4/5/4 rats, 8/8/4 tissues), Wistar‐Kyoto (WKY; n = 4/2/4 rats, 8/8/4 tissues), and Wistar (n = 4/5/4 rats, 8/8/4 tissues) rats were harvested and immunolabeled with PECAM, an endothelial cell marker. Based on vessel lengths, diameters and an assumed pressure drop of 65 mmHg, resistances were calculated using a computational model. For the 7–8 week age group, WKY (34.9 ± 7.4 mmHg/mL) networks had significantly increased resistance compared to SHR (19.7 ± 5.3 mmHg/mL) and Wistar (15.7 ± 5.7 mmHg/mL) networks. No significant differences existed for the 4 and 15–16 week age groups. The results from this study suggest that in hypertension microvascular networks associated with rarefaction do not necessarily have elevated resistances.