title: A post-calcium site of action for HA1004, a novel vasculorelaxant.
abstract: The novel vasorelaxant HA1004 [N-(2-guanidinoethyl)-5-isoquinolinesulfonamide] was investigated with regard to its effects on transmembrane Ca2+ movement in relation to tension development in the rabbit aortic strips. The contractile responses to KCl (40 mM) and norepinephrine (3 X 10(-7) M) were inhibited by HA1004 (1 and 3 X 10(-5) M) (49-78%), whereas the increases in 45Ca efflux (which reflects increases in cytosolic Ca2+ levels) were not affected. Moreover, HA1004 (1 and 3 X 10(-5) M) did not significantly affect 45Ca influx due to KCl stimulation. While HA1004 at 10(-5) M had no effect on norepinephrine-induced 45Ca influx, the drug at 3 X 10(-5) M showed significant inhibition. Based on this and previously reported work, it is concluded that HA1004 inhibits contraction mainly through uncoupling of the Ca-tension relations in vascular smooth muscle.
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004347:Drug Interactions; D007546:Isoquinolines / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D013449:Sulfonamides; D014665:Vasodilator Agents; D014700:Verapamil / Q000494:pharmacology
chemical_list: D007546:Isoquinolines; D013449:Sulfonamides; D014665:Vasodilator Agents; D011189:Potassium Chloride; C043204:N-(2-guanidinoethyl)-5-isoquinolinesulfonamide; D014700:Verapamil; D002118:Calcium; D009638:Norepinephrine