The purpose of this study was to investigate the apoptotic pathway, and the effect and mechanism of IGF-1 (insulin like growth factor 1) as a therapeutic agent, in Adriamycin (ADR) induced cardiomyopathy.

We divided 17 mice into ADR (n=6), ADR +IGF-1 (n=6) and saline (n=5) groups. The following were injected into the intraperitoneal cavity for the specified periods: 2.5 mg/kg of ADR every week for 6 weeks, 0.1 mg/kg of IGF-1 in the 5th and 6th weeks and 10 mL/kg of saline every week for 6 weeks. Transthoracic echocardiography, with a 15MHz linear array, was performed before and after injection of the drugs. A TUNEL assay and immunohistochemical staining for Bax, bcl-2, capase-8 and 9, and western blotting for Bax and bcl-2 were performed on the myocardium.

The fractional shortening decreased (38.5±3.2% before vs. 29.2±5.5% after, p<0.05) and the left ventricular end systolic dimension increased (2.5±0.3 mm before vs. 3.1±0.5 mm after, p<0.05) following the injection of the ADR, but there were no interval changes in the mice treated with saline or ADR+IGF-1. The TUNEL assay showed a higher apoptotic index in the mice treated with ADR than in those treated with saline or ADR+IGF-1 (46±8% in ADR, 0.1±0.03% in control, 22±5% in ADR+IGF-1, p<0.05). The immunohistochemical staining and western blot showed an increase in the expression of Bax, and a decrease in the expression of bcl-2 in the mice treated with ADR than in those treated with ADR+IGF-1 or saline.

The apoptosis caused by the increased expression of Bax, and the decreased expression of bcl-2, was an important pathogenetic mechanism, and the IGF-1 prevents the progression of cardiomyopathy by attenuating the expressions of Bax and bcl-2 in ADR induced cardiomyopaththy.