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

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 < or = 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 (approximately 60 mm Hg). The corresponding maximal (topical papaverine) external diameter (ED) of femoral arteries (N = 5 per group) was reduced (P < or = 0.05) in tail suspended (TS, 511 +/- 47 microm, mean +/- SD) compared with cage sedentary (CS, 615 +/- 89 microm) and food restricted weight-paired (FR, 643 +/- 61 microm) 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 < or = 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 microm) 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 < 0.05), no differences were observed for other vessels among groups. Further, arterial wall thickness increased systemically (overall, P < 0.05; carotid, 24%, P < 0.01; femoral, 28%, P < 0.01) following tail suspension. These findings illustrate adaptation in the structure of conduit arteries to prolonged tail suspension, with diameter altered regionally and wall thickness increased systemically. We suggest that chronic changes in activity patterns can influence arterial structure.