Comparison of the cardiotoxicity of adriamycin and aclacinomycin A in the rat. Optical and electron microscopic study

: Adriamycin (ADM) is a very effective antimitotic agent but its use is limited by its cardiotoxicity. New anthracycline drugs such as aclacinomycin A (ACMA) have been developed and have to be compared with ADM after chronic experimental intoxication. Three groups of randomised rats were compared: the ADM group receiving 2 mg/kg/week X 13 by intraperitoneal injection; the ACMA group receiving 4 mg/kg/week X 13 and a control group: 7 rats. The rats were autopsied at the 20th week. The heart was stopped in diastole and fixed by aortic retroinfusion of glutaraldehide for electronic microscopy (EM). In the ADM group, mean weight fell from the 4th week and mortality was 11/16 at 20 weeks. Voluminous haemorrhagic ascites was associated with peritoneal fibrosis in 12/16. Cardiac failure was observed in 4 cases but on light microscopy (LM) myofibril degeneration was constant and focal without sarcoplasmic reticulum or mitochondrial changes on EM. In the ACMA group the loss of weight occurred at 10 weeks and mortality due to toxicity was nil. There was no cardiac failure; myocytolysis was absent on LM and slight in 4/13 cases on EM with a moderate dilatation of the sarcoplasmic recticulum and presence of numerous residual bodies in the striated skeletal fibres in 5/15 cases. In this study, the ACMA had very little cardio and general toxicity in comparison with ADM. The technique of fixing the heart by retrograde infusion prevents, as far as possible, artefacts on EM affecting mainly the mitochondria.