Morphological remodeling of the intramural coronary resistance artery network geometry in chronically Angiotensin II infused hypertensive female rats

Figures

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  Figure 1. Morphological abnormalities in hypertension a. Control network, plastic cast. b. Hypertensive network, plastic cast. Note undulating course, crossed branches, multiple branching (enlarged in insert). c. and d. Control network, in situ saline perfusion. e. through i. Hypertensive in situ perfused networks. Note broken course of a large branch and parallelly running branches (e), broken course of a large branch and multiple branching (f), multiple branchings (g,h) as well as broken course and uneven diameter (i). Bars, a,b,e, 1000 μm, c,d,f,g,h,i, 500 μm.

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  Figure 2. Analysis of branchings a. Sum of the cube of daughter branch diameters plotted against the cube of the diameter of the mother branch. Bifurcations obeying the Murray law are located on the dotted line. Unaffected by hypertension. b. Interdaughter angle as a function of bifurcation asymmetry. Note that branching angle significantly increases with asymmetry in controls only (with Pearson correlation, p < 0.05). c. Deviation of the axis of the larger daughter branch from that of the mother branch as a function of diameters. Note that in case of larger branches larger deviation of the daughter branch is more frequently found in hypertensives (marked by the ellipse).

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  Figure 3. Analysis of segmental and ring units. a. Number of segments with diameters in different ranges. Pooled data, normalized for 6-6 rats. Note reduced number of segments in the 200–250 μm range in hypertensives. Significantly different with the χ2 probe (p < 0.01). b. Mean segmental length as a function of diameter. Note that short but thick segments are most frequently found in hypertensive networks (p < 0.05 with anova). c. Number of 50 μm ring units in different diameter ranges. Note reduced number of rings in the 200μm, increased number in the 300 μm range in hypertensive networks. Normalized for 6-6 rats. Significantly different with the χ2 probe (p < 0.01). d. The diagram shows the difference of flow distance and direct distance from the orifice for ring units. Note that in hypertensive networks, substantially more distance should be covered by blood flow to reach a certain direct distance than in normal ones (p < 0.01 with two-way anova).

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  Figure 4. Ring unit frequency (color coded) for different diameters and flow distances from the orifice: a two-dimensional histogram. Note that in normal network, smaller arteries are usually farther from the orifice. This pattern has been lost in hypertensive segments: 300 μm arteries dominate the 3–10 mm flow distance range, while the population of 200 μm vessels disappeared.

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  Figure 5. Explanation how the observed geometrical deformities in the hypertensive network could have developed from the original network simply due to morphological shrinkage of certain larger branches while morphological dilation of some microcirculatory units.