Effect of cellular elements on pressure-velocity relationship in mice

The effect of cellular elements in the blood on peripheral vascular function in mice was evaluated using the pressure-velocity relationships in the iliac arteries of 5 wild type (WT) and 3 polycythemic (MH) mice. Pressure was obtained using a fluid filled catheter in the left iliac artery and blood velocity was measured in the right iliac artery using a 20 MHz pulsed Doppler probe. The proximal aorta was then occluded for one minute to allow flow velocity to decay to zero. The pressure-velocity relationship in the diastolic phase was determined before and after aortic occlusion. In both groups the pressure-velocity relationship was almost linear and the slopes were similar. However, the extrapolated zero-velocity intercept was significantly higher for the MH than WT mice before (55.4 +/- 4.0 vs. 36.2 +/- 4.1 mmHg, p<0.01) and after occlusion (50.7 +/- 5.5 vs. 23.8 +/- 3.1 mmHg, p<0.01). Hematocrits were 41%+/-3 in WT and 59%+/-3 in MH mice. These data show that cellular elements in the blood alter the pressure-velocity relationships in peripheral vessels of mice.