PHARMACOLOGICAL DIFFERENTIATION BETWEEN LARGE AND SMALL CORONARY VESSELS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 270  (2) , 255-267
Abstract
There evidently are striking differences between large and small coronary arteries in their responsiveness to adenosine, nitroglycerin and catecholamines. The differential pharmacological responsiveness indicates differences in their excitation-contraction coupling mechanisms. Therefore, agents such as lyotropic anions (SCN-, NO3-, CH3SO4-) known to modulate these processes, and which by themselves do not have an inotropic effect, would be expected to differentially modulate the action of these substances on large and small coronary vessels. To test this hypothesis the modulation by lyotropic anions of the effects of adenosine, nitroglycerin and verapamil on large and small intramural (0.5-0.6 mm diameter) dog coronary arteries was studied. Small vessels apparently are more sensitive to adenosine and verapamil and less sensitive to nitroglycerin than are large vessels. Replacement of Cl- by the lyotropic anions diminished the relaxing effects of adenosine in small vessels with the following order of potency, SCN- > NO3- > CH3SO4- > Cl- .cntdot. NO3-. Replacement of Cl- resulted in almost total bloackade of the adenosine response in small coronary arteries, whereas in large coronary vessels, the effects of nitroglycerin were reduced only 30%. The effects of verapamil in small vessels were slightly depressed whereas in large vessels its effects were unchanged. There seem to be marked differences between the pharmacological responsiveness of large and small coronary vessels, indicating that these differences reside in the nature of their mechanisms controlling Ca2+ translocation.