Comparison of small artery sensitivity and morphology in pressurized and wire-mounted preparations

Two in vitro techniques, the pressurized flow chamber and the wire myograph, commonly employed to study the structure and function of small arteries, were compared. Mesenteric arteries from Wistar-Kyoto (WKY) rats were studied at a transmural pressure (44 +/- 1 mmHg) at which they elicit optimum contraction in each system. Differences in morphological parameters were minor, but there was a marked difference in the vasoconstrictor response of arteries mounted in the wire myograph and pressure system. Endothelium-intact pressurized arteries were significantly more sensitive to norepinephrine and constricted to angiotensin II, whereas wire-mounted vessels did not. These differences in agonist-induced contraction remained after removal of the endothelium. Blockade of amine uptake mechanisms indicated that the difference in norepinephrine sensitivity between the systems resulted from an enhanced influence of neuronal amine uptake in wire-mounted arteries. These data demonstrate that the technique employed has important functional implications for the study of small artery responses in vitro and that the results of investigations into the pathophysiology of small arteries are dependent on the method used and must be interpreted with caution.