The influence of diabetes mellitus and hypercorticism on the wound healing of experimental myocardial infarction in rats.

In diabetic and glucocorticoid-treated rats myocardial infarction is produced by coronary artery ligation. After the ligation was performed the animals were given 3H-thymidine or 3H-proline at different times. The following parameters were determined: number of DNA- and tropocollagen-synthesizing connective-tissue cells both at the infarction border and infarction site; mean silver-grain density above the nuclei or cells; number of mitoses. The labelling and mitotic indices as well as the standard deviation (in percent) from the mean values were calculated. The following results were obtained: 1. The retarded formation of collagen fibres in diabetic animals is caused by a reduced number of tropocollagen-synthesizing fibroblasts and by a diminished synthesizing performance of the individual cells. 2. Glucocorticoids have a pronounced inhibitory effect on granulation-tissue formation, The 3H--thymidine indices are strikingly low. The synthesis of collagen precursors in the fibroblasts is reduced. The release of tropocollagen from the connective-tissue cells is slowed down.