Morphometric analysis of myocardium from copper-deficient pigs

Abstract

Volume densities and ultrastructure of mitochondria and myofibrils from hearts of copper-deficient pigs were evaluated in two studies. Weaned male pigs (21 d of age) were fed purified diets with adequate copper (Study 1: 7.1 mg Cu/Kg, n=4; Study 2: 8.4 mg Cu/Kg, n=6) or no copper added (Study 1:1.2 mg Cu/kg, n=4; Study 2: 0.84 mg Cu/Kg, n=5). Pigs in both studies fed the copper-deficient diet developed symptoms of copper deficiency, including decreased levels of the micronutrient in liver, heart and plasma, and increased heart to body weight ratio. Morphometric evaluation revealed a significant increase in mitochondrial volume density and in the ratio of mitochondria to myofibril volume densities in copper-deficient hearts. The myofibril volume density and the heart to body weight ratio was positively correlated in study 1, suggesting that the enlarged hearts of the Cu deficient pigs were due to an increase in the volumes of both mitochondria and myofibril compartments. Mitochondria in areas appeared vacuolated and cristae were fragmented in the copper-deficient pig myocardium as opposed to the normal parallel array of these structures. Separated myofilaments and deposits of glycogen granules were also evident in the copper-deficient pig heart. These results suggest that copper-deficiency alters the ultrastructural characteristics of the pig heart in a similar manner as previously reported for the laboratory rat.