Effects of vesnarinone, a novel orally active inotropic agent with an immunosuppressive action, on experimental cardiac transplantation in rats

Background. Vesnarinone (VES) has been used for treatment of patients with congestive heart failure. In addition to inotropic effects, it seems to have immunosuppressive action. We tested the hypothesis that VES suppresses graft rejection, inotropic dysfunction caused by early rejection, and chronic coronary obstruction in a heterotopic rat cardiac transplantation model. Methods. (1) To study acute rejection, hearts from Lewis-Brown Norway (LBN) rats were transplanted into Lewis rats, which were treated with or without VES (50 or 100 mg/kg/day orally). (2) In a functional study, LBN hearts with or without VIES (100 mg/kg/day) were isolated and perfused on day 3 after transplantation to assess inotropic response to isoproterenol (3x 10^-8 M). (3) To study chronic rejection, Lewis hearts were transplanted into Fisher 344 rats, which were treated with or without VES (50 mg/kg/day) for 90 days. Coronary obstructive disease was assessed by morphometric analysis. There were five to six animals in each group. Results. (1) VES (100 mg/kg/day) prolonged LBN heart survival (11.7±0.7 vs. 9.6±0.7 days in control; P<0.05). (2) Left ventricular developed pressure was depressed in transplanted hearts regardless of VES treatment (84±12, 90±8 vs. 144±16 mmHg in untransplanted hearts; P<0.01). The developed pressure after administration of isoproterenol in VES-treated hearts (184±20 mmHg) was higher than transplanted hearts without VES (118±16 mmHg; P<0.05), and similar to untransplanted hearts (203±27 mmHg; P=NS). (3) Transplanted hearts treated with or without VES showed similar grades of rejection (2.0±0.3 vs. 2.6±0.2; P=NS), intimal area (6,996±3,186 vs. 13,441±5,165 μm²; NS), and coronary luminal obstruction (45±16% vs. 67±14%; NS). Conclusions. VES produces mild prolongation in survival of rat heart grafts, but has no significant effect on chronic graft atherosclerosis. VES preserves the positive inotropic effects of isoproterenol that are otherwise deteriorated by early acute rejection.