Response of large and small coronary arteries to nitroglycerin, NaNO 2 , and adenosine.

SCHNAAR, RONALD L., AND HARVEY V. SPARKS. Response of large and small coronary arteries to nitroglycerin, NaNO2, and adenosine. Am. J. Physiol. 223(l) : 223-228. 1972.-Large (2 mm od) and small (.5 mm od) coronary artery strips were mounted side by side in a muscle bath. KC1 concentration was brought to 35 mM to produce tone and isometric tension was measured. Responses were expressed as the percent of the maximum relaxation caused by calcium-free physiological salt solution. NaNOz and nitroglycerin caused greater relaxation of large vessels than small (P < 0.05). Adenosine caused greater relaxation of small vessels than large vessels (P < 0.05). Depolarization with an isotonic high potassium (100 mM K&04) solution did not reduce the relaxation in response to nitroglycerin or adenosine, suggesting that relaxation can occur without changes in the electrical state of the cell membrane. The effects of adenosine and nitroglycerin on Ca++-induced contraction suggest that the differential effect of adenosine on large and small arteries may be explained by different effects on Ca ++ flux, but that the differential effect of nitroglycerin may not be explained in this way. This study supports in situ work suggesting differences in the response of vascular smooth muscle of large and small coronary arteries to nitroglycerin.