TISSUE ANGIOTENSIN I-CONVERTING ENZYME-ACTIVITY IN AGING HAMSTERS WITH AND WITHOUT CARDIOMYOPATHY

The purpose of this study was to determine tissue angiotensin I-conver ting enzyme (ACE) activity in ageing hamsters with and without cardiom yopathy, and the factors that regulate its activity in vitro. We found that ACE activity was significantly increased in the heart and signif icantly decreased in the lung of ageing hamsters with hereditary cardi omyopathy in comparison to age/genetically-matched controls (P < 0.05) . Kidney and cheek pouch ACE activity was similar in both groups. Lisi nopril inhibition curves of tissue ACE activity were similar in ageing hamsters with and without cardiomyopathy. In both groups, tissue ACE activity was dependent on chloride anion concentration in the assay bu ffer. Substituting citrate for chloride abrogated, in part, this respo nse. We conclude that cardiomyopathy is associated with significant ch anges in cardiac and lung ACE activity in ageing hamsters in compariso n to age/genetically-matched controls. However, regulation of tissue A CE activity in vitro is similar in both groups.