Mechanical properties of the copper-deficient rat heart

Copper deficiency is known to induce cardiac hypertrophy, cardiac morphologic lesions and altered electrocardiograms. These findings suggest that copper deficiency may also influence the mechanical properties of the myocardium. In the present study, weanling albino rats were fed a copper-deficient (-Cu) diet and compared to rats fed the same diet but with copper supplementation in the drinking water (+Cu). Rats were studied during a 1-week period following 4.5-5.5 weeks of treatment. When compared to +Cu rats, the -Cu rats exhibited characteristic signs of copper deficiency, such as reduced body weight, hypoceruloplasminemia, depressed hematocrit, low copper and elevated iron concentration in the liver. The -Cu rats also exhibited cardiac hypertrophy and both a dilution and depletion of left ventricular norepinephrine. Hearts were perfused and paced at both 27 degrees and 37 degrees. When compared to hearts from +Cu rats, the -Cu hearts: 1) had lower spontaneous heart rates, 2) had decreased coronary resistance, 3) gained significant weight during perfusion, 4) consumed more oxygen per unit pressure developed, and 5) developed less systolic pressure with a reduced rate of pressure development. However, the time to peak pressure development, one-halt relaxation time, and refractory period were not affected. The altered characteristics of the copper-deficient myocardium may be due to changes in the elastic properties of the muscle, aberrant energy metabolism or norepinephrine depletion.