Effects of angiotensin converting enzyme inhibitor and angiotensin II type1 receptor blocker on cardiac dysfunction induced by isoproterenol in dogs

We examined whether angiotensin converting enzyme (ACE) inhibitors and angi otensin II type I receptor blockers (ARB) prevent isoproterenol (ISO)-induc ed left ventricular (LU) dysfunction in dogs. The effects of a large dose o f ISO, 1 mug/kg/min, 3 h infusion, were investigated in three groups with s imultaneous infusion of an ACE inhibitor (quinaprilat), ARB (candesartan) o r saline. ISO infusion significantly decreased LV dP/dt, LV ejection fracti on and LV fractional shortening, and significantly increased tau, the time constant of isovolume relaxation of Lv, and IV end diastolic pressure. All of these changes were significantly attenuated in both the ACE inhibitor an d ARB groups, especially in the ARB group. Serum levels of creatinin kinase isoform MB, lactate dehydrogenase and lipid peroxide were significantly in creased by ISO. However, the increases in these markers of myocardial damag e were significantly diminished by simultaneous infusion of an ACE inhibito r or ARB, especially by ARB. In conclusion, an ACE inhibitor and ARB preven t LV systolic and diastolic dysfunction as well as myocardial damage induce d by excess beta -adrenergic stimulation.