Changes in the collagen of rat heart in copper-deficiency-induced cardiac hypertrophy

Groups of rats were maintained from weaning on copper-supplemented or copper-deficient diets. After 2, 4, 6, 8 or 12 weeks animals were killed, their hearts were removed and the solubility and phenotype composition of the collagen of the hearts was studied. In the hearts from the copper-supplemented animals 35 to 45% of the collagen could be extracted after two treatments with pepsin but up to 74% could be extracted from the hypertrophied copper-deficient hearts. Almost all of the increase in the soluble material was found in the first pepsin extract. Electrophoretic analysis of the extracts showed that in the copper-supplemented hearts the ratio of Type III/Type I collagen increased about threefold between 2 and 6 weeks after weaning but by 8 weeks it had returned to about the level found at 2 weeks and was maintained at this level to the end of the experimental period. In the copper-deficient hearts the ratio of Type III/Type I collagen had increased about fivefold by 6 weeks after weaning and from 8 weeks to the end of the experimental period it remained at two to three times the value found in the copper-supplemented hearts. There was an indication that the relative proportion of Type V collagen was reduced in the copper-deficient hearts. The possible significance of these results in relation to the known pathological effects of copper deficiency on the cardiovascular system is discussed.