Nucleolar organizer regions in cardiac lesions induced by doxorubicin.

The use of the argyrophilic (Ag) staining technique for nucleolar organizer regions (NORs) revealed nuclear changes in myocytes of the left atrium of 10 rats treated twice a week for 6 weeks with doxorubicin (1 mg/kg body weight) iv and sacrificed after 6 weeks without treatment. The changes were easily detected qualitatively and further assessed by quantification. Cardiac myocytes of doxorubicin-treated rats had larger nuclei and/or a larger quantity of AgNORs that were either dispersed in a number of small dots or clustered in rounded, rod-shaped, or tortuous large structures. AgNOR alterations may reflect a defect of nucleolar association leading to an impairment of protein synthesis that could be involved in doxorubicin cardiotoxicity.