Differential contractile responses of pressurized porcine coronary resistance-sized and conductance coronary arteries to acetylcholine, histamine and prostaglandin F2 alpha.

The reactivities of porcine resistance-sized arteries (270 microns 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 EC50 was 0.19 microM. Constrictions to histamine and prostaglandin F2 alpha (PGF2 alpha), 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 PGF2 alpha, respectively. Corresponding EC50 values were 0.58, 2.8 and 2.9 microM. The significant differences in reactivity between resistance and conductance arteries underscore the potential importance of regional specialization in the coronary blood flow regulation.