Arterial morphology and blood volumes of rats following 10-14 weeks of tail suspension

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Abstract
We hypothesized that the structure of systemic arteries would be altered following 10-14 wk of hindlimb unloading (tail suspension) in female Sprague-Dawley rats. Tail suspension resulted in atrophy of the soleus muscle(P ≤ 0.01) but no significant differences in the mass of the extensor digitorum muscle, heart, or adrenal glands. In anesthetized rats, there was no difference between groups in arterial pressure (≈60 mm Hg). The corresponding maximal (topical papaverine) external diameter (ED) of femoral arteries (N = 5 per group) was reduced (P ≤ 0.05) in tail suspended (TS, 511 ± 47 μm, mean ± SD) compared with cage sedentary (CS, 615 ± 89 μm) and food restricted weight-paired (FR, 643 ± 61 μm) groups. Neither hematocrit, red cell, plasma, nor total blood volume differed among groups. Following systemic vasodilation with papaverine, progressive arterial inflation with liquid silicon rubber (Microfil) revealed a reduction in both ED and distensibility of the femoral artery (P ≤ 0.05). To determine the effects of tail suspension on systemic arterial morphology, the vasculature of additional rats was perfusion fixed at 80 mm Hg during vasodilation. Cross sections(thickness, 8 μm) of the carotid, axillary, iliac, and femoral arteries were then evaluated. Whereas the internal diameter of femoral arteries was smaller in TS than in CS (P P