Effects of 4-Aminopyridine and Tetraethylammonium on Relaxant Responses of Isolated Dog Coronary Arteries to 2-Nicotinamidoethyl Nitrate (SG-75)

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Effects of 4-aminopyridine (4-AP) and tetraethylammonium (TEA) on vasodilator actions of 2-nicotinamidoethyl nitrate (SG-75) were investigated using isolated dog coronary arteries. SG-75 10-8-10-4Gm/ml produced concentration-dependent relaxations of coronary arterial strips which were contracted with potassium 30mM or prostaglandin (PG) F2α 10-6Gm/ml. Both 4-AP 5×10-4Gm/ml and TEA 1.6×10-3Gm/ml produced further contractions of the strips under potassium- or PGF2α-contracture. The potency to constrict the strips was greater in 4-AP than in TEA. 4-AP 5×10-4Gm/ml and TEA 1.6×10-3Gm/ml did not affect the SG-75-induced relaxations of the strips under potassium-contracture, but significantly depressed them under PGF2α-contracture. In the strips under a resting state, 4-AP 5×10-4Gm/ml increased tension and produced oscillations in their contractions, but TEA 1.6×10-3Gm/ml did not. Results suggest that SG-75 may display its relaxant effect on isolated dog coronary arteries in part through an increase in potassium conductance.
International Heart Journal刊行会の論文