Paramagnetic changes during development of a transplanted AKR-J leukemia in mice as measured by electron spin resonance.

Paramagnetic changes occurring during tumor develop ment were studied in the mouse AKR leukemia (trans planted) model system using electron spin resonance. Para magnetic changes were found only in blood and in organs directly involved by the leukemic cells. The change in blood consisted of an increase in a paramagnetic transition element complex, and occurred prior to the tissue changes. In the liver, both free radicals and normally occurring tran sition elements decreased when the liver became exten sively infiltrated by the leukemic cells. Similar results were found in the spleen, except that in the spleen there also was an increase of a paramagnetic transition element or ele ments, with an apparent g factor near g = 2.003, plus the development of additional hyperfine structure in propor tion to tumor involvement. An early rise in free radicals, which has been reported as characteristic of tumor develop ment, was not observed in these studies.