Effects of K+ channel blockers on the relaxation of isolated rat aorta by nitroglycerin

• Published in: Japanese Journal of Pharmacology 1994, Vol.64 (suppl.1), p.154-154
• Main Authors: Nakazawa, Mikio, Xiu-Jun, Pi, Imai, Shoichi
• Format: Article
• Language: eng ; jpn
• ISSN: 0021-5198
• DOI: 10.1016/S0021-5198(19)50258-X

We investigated involvement of K^+ channel activation in the relaxation by nitroglycerin (NG) of the ring preparation of the isolated rat aorta pre-contracted by 0.3 μM of noradrenaline. We used tetraethylammonium (TEA) , charybdotoxin (ChTX), apamine and glibenclamide to block various types of K^+ channels. The concentration-relaxation curve to NG had two components with EC_50 value of 103 nM and 12 μM. TEA (1 and 4 mM) inhibited non-competitively the high affinity component and the low affinity one in an apparently competitive manner. Other blockers of K^+ channels caused no significant effect on the relaxation by NG. Relaxation by sodium nitroprusside (SNP) was competitively inhibited by TEA (1 and 4 mM) and charybdotoxin (10 and 100 nM). These results suggest that the activation of the Ca^2+ -activated large conductance K^+ channel may be involved in the SNP-induced relaxation but not in the NG-induced one in the rat aorta.