Effects of clofilium on cardiovascular tissues from normo- and hypertensive rats

1. The overall aim was to test whether clofilium has some potential as a positive inotrope for heart failure. We used Wistar Kyoto normotensive rats (WKY) and spontaneously hypertensive rats (SHRs) and studied the effects of clofilium on isolated blood vessels, left ventricular action potentials and left ventricular contractility. 2. Clofilium at < or = 10(-6) M had no effect on WKY portal vein contractions and at < or = 3 x 10(-4) M had no effect on WKY or SHR quiescent mesenteric and intralobar pulmonary arteries. 3. Clofilium at 10(7) - 10(-5) M prolonged the WKY left ventricular action potentials and with 10(-6) and 10(-5)M this included after-depolarizations. 4. Clofilium at < or = 3 x 10(-5) M augmented the peak force, prolonged the contractions and did not cause arrhythmias in the absence and presence of isoprenaline on left ventricle strips from 12-month-old WKY. 5. The 12-month-old SHR has hypertrophy of the left ventricle with reduced peak force and prolongation of relaxation. The effects of clofilium on 12-month-old SHR left ventricle contractility were similar to those in the age-matched WKY. 6 In summary, clofilium has positive inotropic effects on the rat left ventricle that are maintained in hypertrophy. Clofilium does not have effects on blood vessels that would be detrimental in heart failure. Clofilium prolongs the rat left ventricle action potential and causes after-depolarizations. The pro-arrhythmic potential of clofilium, however, makes it unlikely that it could be used as a positive inotrope in the treatment of heart failure.