AN INVESTIGATION OF BONE-MARROW AND TESTICULAR CELLS IN-VIVO USING THE COMET ASSAY

The effects of the mutagens, cyclophosphamide (CP), ethyl methanesulph onate (EMS), bleomycin (BLM) and the testicular toxin ethylene glycol monomethyl ether (EGME) in bone marrow and testicular cells have been compared in the alkaline COMET assay. Sprague-Dawley rats were adminis tered by gavage with 50, 100 and 150 mg/kg body weight (bw) of CP; 100 , 200 and 300 mg/kg bw EMS; 50, 100 and 150 mg/kg bw BLM and 500, 1000 and 1500 mg/kg bw EGME. Effects were examined at week 2 after treatme nt for CP, EMS BLM and EGME and at weeks 5 and 6 for EGME. Bone marrow cells were removed and separated by aspiration of the femur and testi cular cells by decapsulation of the testis, treating with collagenase followed by trypsin. Various statistical methods were used to analyse the data. For CP there was an increase in damage above control values for bone marrow at 50 mg/kg bw which decreased at 100 mg/kg bw, and th ere was mortality of the animals at 150 mg/kg bw. A similar response w as found in the testicular cells. For EMS and BLM, there were only occ asional slight increases in damage in bone marrow and testicular cells . Two studies were conducted with EGME. In the first, where effects we re examined at week 2 after treatment, there was an increase in damage in bone marrow cells, but a larger response was observed in testicula r cells. In the second study where effects were examined at weeks 5 an d 6 after treatment, bone marrow and testicular cells were not affecte d. The overall results showed that damage persisted for 2 weeks after treatment with CP and EGME but not in weeks 5 and 6 for EGME. Various statistical methods were used to analyse the data. Statistically signi ficant responses were produced after treatment with CP and EGME and we re dose-related for EGME, but after treatment with EMS and BLM statist ical increases were sporadic. These results suggest that the assay is useful for measuring DNA damage and its persistence, and for comparing the sensitivity of different target organs in vivo.