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Myofibrillar, Mitochondrial and Valvular Morphological Alterations in Cardiac Hypertrophy among Copper-Deficient Rats¹

Denis M. Medeiros^*, Donna Bagby, George Ovecka^** and Richard McCormick

^* Department of Human Nutrition and Food Management, The Ohio State University, Columbus, OH 43210 Department of Zoology and Physiology ^** Department of Home Economics Department of Animal Science, The University of Wyoming, Laramie, WY 82071

Histological aspects of Cu-deficient hypertrophied rat hearts were evaluated to determine causal factors. Twenty-four male weanling rats were fed either Cu-adequate (8.0 mg/kg diet) or Cu-deficient (0.4 mg/kg diet) diets until 9 or 11 wk of age. Copper-deficient rats had increased mitochondrial:myofibrillar ratios compared with Cu-adequate rats. Mitochondria were vacuolated. Cristae seemed fragmented and matrix seemed translucent and they tended to distort the myofibrils. Glycogen granules and lipid droplets were more frequently observed in Cu-deficient rats. When the Cu-deficient rats were examined separately, the larger hearts in the older rats had smaller mitochondrial:myofibrillar ratios, but had larger myofibrillar volume densities. Valves from Cu-deficient rats had less connective tissue and seemed fragmented in areas. In 9-wk-old Cu-deficient rats, there was a negative correlation between heart: body weight ratios and bicuspid valve scores, whereas 11-wk-old rats demonstrated the same relationship for tricuspid valves with myofibril volume density. These results suggest that there are two components contributing to cardiac hypertrophy in copper deficient rats: 1) an enlarged mitochondrial area and 2) myofibrillar enlargement. Hematocrit values did not seem to be related to cardiac hypertrophy.

KEY WORDS: • cardiac hypertrophy • copper deficiency • tricuspid and bicuspid valves • mitochondria • myofibrils • rats

¹ Supported by the National Science Foundation, Grant No. R11-8610680, and the National Heart, Lung and Blood Institute, Grant No. 5 R01 HL34286, to D. M. Medeiros.

Manuscript received 23 April 1990. Revision accepted 24 September 1990.