The effects of acidosis and alkalosis on long bone vascular resistance.

This study used an ex vivo perfusion model to investigate the direct effects of acidosis and alkalosis on the vascular resistance of the canine tibia. Baseline vascular resistance (BVR) and the vascular smooth muscle response to bolus doses of norepinephrine (NE) (0.025-3.2 nmol) and periarterial sympathetic nerve stimulation (NS) (10-25 Hz: 9 V, 2 ms pulses, 10 s) were studied. In Group I, these parameters were measured at normal pH (duration 7.34-7.44) and then during acidosis (pH 7.2-7.33). In Group II, they were measured at normal pH and then during alkalosis (pH 7.47-7.58). In Group III (control), they were measured serially at a normal pH. Alkalosis increased BVR by 56% (p < 0.0001). Acidosis attenuated (18% reduction) and alkalosis enhanced (66% increase) the vasoconstrictor action of NE (p < 0.0001). Acidosis also attenuated (11% reduction) the effect of sympathetic NS (p = 0.012). It is concluded that perfusion pH influences the sensitivity of long bone resistance vessels to circulating NE and sympathetic NS. Thus, local concentration of hydrogen ions may provide bone with a mechanism to autoregulate blood flow.