Continuous control of the lumen of feline conduit arteries by blood flow rate.

Dilatation of conduit arteries induced by increased blood flow was studied in feline femoral, common carotid, or renal arteries. The outer diameter of the arteries perfused under stabilised transmural pressure conditions was continuously measured with a contact capacitance type transducer. A rise in blood flow rate was shown to induce arterial dilatation, the magnitude of which depended linearly on the extent of flow increase over a wide range of flow rates (usually from 10-15 to 35-50 ml.min-1). Increase in flow above this range caused a smaller increase in diameter followed by a plateau phase. The maximal (mean(SEM] flow induced increase in arterial diameter was 25.8(2.8)% for the femoral, 25.5(2.2)% for the common carotid, and 24.6(5.1)% for the renal artery. This dilatation almost completely compensated for the increase in flow, causing a practically unchanged pressure difference along the arteries. A pronounced dilator response to an increase in blood flow rate as small as 1 ml.min-1 could be recorded for all flow rates where the diameter-flow relation was linear. Flow induced dilatation persisted during perfusion with a solution free of vasoactive substance. Thus in the arterial wall some mechanism provides effective continuous control of the lumen and, consequently, hydraulic resistance of the arteries in response to increases in blood flow.