Comparison of relaxation responses of vascular and non-vascular smooth muscle to endothelium-derived relaxing factor (EDRF), acidified sodium nitrite (NO) and sodium nitroprusside.

Smooth muscle relaxant activity of endothelium-derived relaxing factor (EDRF) released from columns of cultured bovine endothelial cells by bradykinin (0.1-3 nmol/l) was measured in four non-vascular preparations: guinea-pig taenia caeci, guinea-pig trachea, rat stomach (fundus) and rat anococcygeus. Each preparation was contracted to a steady level of force with a variety of agonists such that they relaxed optimally to sodium nitroprusside (SNP). The EDRF-induced relaxations in each preparation were compared with those obtained in de-endothelialized ring preparations of greyhound coronary artery by means of paired bioassays run in parallel. EDRF released from the endothelial cell columns caused 80-100% relaxation of the coronary artery, 40-80% in the guinea-pig taenia caeci, 50-70% in the rat anococcygeus, 5-8% in the guinea-pig trachea and was undetectable in the rat stomach strip. By comparison, SNP caused maximal relaxation in all tissues compared with the coronary artery. In separate organ bath experiments the sensitivity to nitric oxide (NO: generated by adding acidified solutions of NaNO2) and SNP was compared in each preparation. SNP caused maximal relaxation in all tissues with the following order of potency: dog coronary artery greater than guinea-pig trachea greater than guinea-pig taenia = rat anococcygeus greater than rat stomach strip. In contrast, the concentration of acidified NaNO2 (NO, 300 nmol/l) that caused 96 +/- 4% relaxation in the dog coronary artery caused 84 +/- 7% and 48 +/- 1% relaxation in the taenia and anococcygeus respectively. No response attributable to NO was detected in either the trachea or rat stomach strip.(ABSTRACT TRUNCATED AT 250 WORDS)