Antihypertensive and vasorelaxant effects on KRN2391 in spontaneously hypertensive rats

In vitro and in vivo vasodilating effects of KRN4884, Ki1769 and Ki3005, pyridinecarboxamidine derivatives

The vasodilating potencies and mechanism of action of a novel pyridinecarboxamidine derivative, KRN4884 [5-amino-N-[2-(2-chlorophenyl)ethyl]-N'-cyano-3-pyridinecarboxamidine ] were compared with those of Ki1769 [N-cyano-N'-(2-phenylethyl)-3-pyridinecarboxamidine] and Ki3005 [N-[2-(2-chlorophenyl)ethyl]-N'-cyano-3-pyridinecarboxamidine] in rat isolated aortas and in anesthetized normotensive rats. In vitro. KRN4884 (10(-10)-10(-6) M). Ki1769 (10(-8)-10(-5) M) and Ki3005 (10(-10)-10(-6) M) produced concentration-dependent relaxations. KRN4884 was about 100- and 10-fold more potent than Ki1769 and Ki3005, respectively. The relaxant effects of these compounds were antagonized by glibenclamide. In vivo, KRN4884 (1-10 micrograms/kg, intravenously [i.v.]), Ki1769 (10-100 micrograms/kg, i.v.) and Ki3005 (3-30 micrograms/kg, i.v.) produced dose-dependent decreases in mean blood pressure with slight increases in heart rate. At 10 micrograms/kg, i.v., the hypotensive effect of KRN4884 was about the same as that of Ki3005 and about 5-fold more pronounced than that of Ki1769. The hypotensive action remained for a longer period after KRN4884 administration. In rats pre-treated with glibenclamide (20 mg/kg, i.v.), the hypotensive effect of KRN4884 was abolished. These results suggest that the effect of KRN4884 in vitro and in vivo is based on its K channel opening action and that the in vitro vasorelaxant effect of these compounds in aortic rings does not predict their relative hypotensive effect in vivo.