The influence of hyperthyroidism and hypothyroidism on the wound healing of experimental myocardial infarction in the rat.

In hyperthyroid and hypothyroid rats myocardial infarction was produced by coronary artery ligature. At different times following the ligature the animals were given 3H-thymidine or 3H-proline. The following parameters were determined: the number of DNA- and tropocollagen-synthesizing connective-tissue cells at the infarction border and at the infarction site; the mean silver-grain density above the nuclei or cells; the duration of one cell cycle; and the number of mitoses. The labelling and mitotic indices as well as the percentage of the standard deviation from the mean values were estimated. The following results were obtained: 1. In hyperthyroidism wound healing is accelerated. The number of DNA-synthesizing connective-tissue cells is increased. The cell-cycles are shorter. The release of tropocollagen by the fibroblasts takes place at a strikingly fast rate. 2. In hypothyroidism wound healing is delayed. The 3H-thymidine and mitotic indices are lowered. The release of tropocollagen is slowed down. The granulation tissue contains localized accumulations of mucopolysaccharides.