The effect of cis-platinum (II) diamminodichloride on bone marrow.

were analyzed in mice. Cell counts in unit volumes of bone marrow, mitotic indices, and relative frequencies of individual elements were estimated 1, 3, 6, and 24 hr and 3, 6, and 10 days after drug administration. It was found that changes in mitotic index occurred prior to changes in cell count. Mitotic index and the cell count decreased from Hr 1 reaching minimum values after 24 and 72 hr, respectively. Normal values were then reached after oscillations. Only small changes were observed in erythroblasts, whereas more mature normoblasts decreased on Day 3 and later increased. With myeloid cells, pronounced changes occurred in the number of more mature forms. Oscillations of decreasing amplitude, observed in lymphocytes, monocytes, and megakaryocytes, were charac terized by a high rise early after administration followed by a decrease below control values and, finally, a trend toward increase to normal values. Most probably, the slight oscilla tions extended longer than the 10-day period and will be studied later. We concluded that the observed changes after a dose of 8 mg/kg corresponded to, for example, rather low doses of X-irradiation.