Differential Contractile Responses of Pressurized Porcine Coronary Resistance-Sized and Conductance Coronary Arteries to Acetylcholine, Histamine and Prostaglandin F<sub>2α</sub>

The reactivities of porcine resistance-sized arteries (270 µm o.d.) and conductance coronary arteries (4.2 mm o.d.) were compared in the presence of a functional and morphologically intact endothelium using a pressurized in vitro preparation. In resistance vessels, acetylcholine (ACh) produced maximal diameter reductions of 42 % and the EC<sub>50</sub> was 0.19 µM. Constrictions to histamine and prostaglandin F<sub>2α</sub> (PGF2«), however, were either absent or minimal. In contrast, maximum diameter constrictions of conductance vessels were 19, 33 and 22% in response to ACh, histamine and PGF<sub>2α</sub>, respectively. Corresponding EC<sub>50</sub> values were 0.58, 2.8 and 2.9<i>µM. </i>The significant differences in reactivity between resistance and conductance arteries underscore the potential importance of regional specialization in the coronary blood flow regulation.