Changes in marrow myelopoietic and lymphoid cell counts after repeated cyclophosphamide administration in the rat.

Rat marrow myeloid and lymphoid counts were estimated after repeated doses of cyclophosphamide injected intraperitoneally. It was found that in order to evaluate the bone marrow response, a quantitative approach is a necessity. Myelotoxic and lymphotoxic effects in the bone marrow following repeated doses of cyclophosphamide were markedly similar to suppression which followed the restriction of food consumption. Relationships between rat white blood and marrow counts were analyzed. Convenience of determination of marrow cellularity for measurement of myelotoxic effects is discussed with respect to studies with repeated administration of cytostatic agents.