Growth hormone interferes with the progression of myocarditis in rats

In this study, we investigated whether recombinant human growth hormone (rh GH) influences the progression of myocarditis. We induced experimental auto immune myocarditis in F344 rats by subcutaneous injection of cardiac myosin , and divided the rats into three groups: (1) control group, saline injecti on; (2) pre-treated group, subcutaneous injection of rhGH (100 mIU/rat/day for 10 days) before induction of experimental autoimmune myocarditis; and ( 3) post-treated group. subcutaneous injection of rhGH (100 mlU/rat/day for 10 days) after induction of experimental autoimmune myocarditis. On the 35t h day after induction of experimental autoimmune myocarditis, all rats were sacrificed and the hearts were examined. The increase in body weight was s maller in the control group than the pre-treated soup and the rate of heart weight/body weight was larger in the control group than in the two treated groups. Histopathologically, rats in the control group showed multifocal i nfiltration by inflammatory cells, mainly neutrophils, lymphocytes and macr ophages, extensive fibrosis, and a higher proportion of mast cells in the i nflammed region. In contrast, rats in the two treated groups showed only mi nor changes. We found that rhGH did not influence the distribution of lymph ocytes in peripheral blood in the three groups, and that rhGH induced G1 ch eckpoint dysfunction, thereby arresting the cell cycle in G1 and inhibiting the proliferation of mast cells in vitro. These findings suggest a possibl e role for mast cells in the progression of myocarditis and the rhGH may be a candidate for use as a new tool to treat myocarditis. (C) 2001 Elsevier Science B.V, All rights reserved.