POTENTIAL PROTECTIVE EFFECTS OF MELATONIN ON BONE-MARROW OF RATS EXPOSED TO CYTOTOXIC DRUGS

Myelosuppression is the most serious, dose limiting, toxicity of cytot oxic drugs. Efforts to protect the bone marrow have been only variably successful, and no agreement exists on holy to approach this problem. Melatonin, the major hormonal product of the pineal gland, is suppose d to have both chemoprotective and myelostimulatory effects. This expe rimental study was carried out to test these two effects on the bone m arrow of rats, daily intraperitoneally injected with 100 mu g melatoni n. Injection of 10 mg aracytin for 10 days produced a significant (P < 0.01) decrease in red blood cells count (RBCs), total leucocytic coun t, as well as platelets count. When melatonin was injected along with aracytin, it would significantly increase (P < 0.05) RBC count and (P < 0.01) blood platelet count. Injection of melatonin after aracytin tr eatment would significantly increase (P < 0.01) RBC, total leucocytic and platelet counts in comparison with rats treated with aracytin only . Thr effects of melatonin were more clear in rats treated with it aft er aracytin injection than those treated with melatonin and aracytin a t the same time. Furthermore, it was found that aracytin produced a si gnificant (P < 0.01) decrease in serum total proteins, albumin, and si gnificantly increased the (P < 0.01) albumin/globulin ratio. Melatonin injection would significantly increase (P < 0.01) total protein, glob ulin, and significantly decrease (P < 0.01) the albumin/glubulin ratio when injected either with aracytin or after aracytin treatment. These results indicate that melatonin protects bone marrow, lymphoid tissue s from damaging effect of cytotoxic drugs, as well as stimulating the suppressed bone marrow. (C) 1998 Elsevier Science Inc.