Flow-induced vasodilation in the ferret lung

Chammas, Joseph H., David. A. Rickaby, Margarita Guarin,John H. Linehan, Christopher C. Hanger, and Christopher A. Dawson. Flow-induced vasodilation in the ferret lung. J. Appl. Physiol. 83(2): 495-502, 1997.To examinethe possibility that shear stress may be a pulmonary vasodilatorstimulus, we studied the effect of changing blood flow on the diametersof small pulmonary arteries in isolated perfused ferret lung lobes. Thearteries studied were in the ~0.3- to 1.3-mm-diameter range, and thediameters were measured by using microfocal X-ray imaging. Thediameters were measured at two flow rates, 10 and 40 ml/min, with theintravascular pressure in the measured vessels the same at the two flowrates as the result of venous pressure adjustment. The response to a change in flow was studied under both normoxic and hypoxic conditions. Hypoxia was used to elevate pulmonary arterial tone to increase thelikelihood of detecting a vasodilator response. Under normoxic conditions, changing flow had little effect on the arterial diameters, but under hypoxic conditions the arteries were consistently larger atthe higher flow than at the lower flow, even though the distending pressure was the same at the two flow rates. The results are consistent with the hypothesis that shear stress is a pulmonary vasodilator stimulus.