The external diameter of the artery (1.08 +/- 0.04 mm) predominantly supplying the gracilis muscle was monitored in situ in 12 dogs under thiopental anaesthesia using a contact inductive transformer. The blood flow in the artery could be controlled by an arteriovenous shunt. After a latency of 10.6 +/- 0.7 s, an increase of blood flow through the artery from 4.0 +/- 0.3 to 45.0 +/- 3.4 ml.min-1 induced an increase in its diameter by 44.9 +/- 3.6% of the resting value (p less than 0.001). When the blood flow-rate was reduced to the initial level, the artery constricted with a half-recovery time of 307.2 +/- 30.7 s. The amplitude and the time course of the arterial dilation were identical when the blood pressure at the site of diameter measurement decreased or remained unchanged. The dilation became maximal at blood flows corresponding to the peak of reactive hyperaemia in the gracilis muscle after 2 min arterial occlusion. It is being suggested that the blood flow-induced dilation ensures autostabilization of conduit artery function.

Institute of Normal and Pathological Physiology Slovak Academy of Sciences Bratislava