Magnetic susceptibility and electron spin resonance absorption spectra of mouse melanomas S91 and 591A.

A study of magnetic susceptibility and electron spin resonance (E.S.R.) spectra of Cloudman S91 and S91A melanomas and various mouse tissues was correlated with trace-metal analysis and known biochemical reactions. Average magnetic moments obtained from temperature-dependence studies showed the following order for tissues: S91>S91A>leg muscle. These results indicated a similar order in the relative concentration of magnetic species (free radicals and/or paramagnetic ions) and were confirmed by E.S.R. The E.S.R. spectra at different power levels showed that the free radical activity and the Cu2+ and Fe3+ activity attributed to different signals was generally higher in S91 than in S91A, which did not show an Fe3+ type signal. Normal tissues such as liver, spleen, heart, kidney, brain, and leg muscle showed varying amounts of free radical activity but not signals attributable to paramagnetic ions. E.S.R. spectra and trace-metal analysis at different stages of S91 tumor growth indicated a systematic increase in the free rad cal activity, total copper and iron concentrations, and paramagnetic ions, presumed to be Cu2+ and Fe3+. The S91A melanoma showed increase in total copper, but not in free radical and paramagnetic ion (CU2+) activity after the initial growth. Correlation of these findings with known biochemical reactions suggests that the free radical activity may be attributed partly to melanin and intermediates of various enzymatic reactions. Presumed paramagnetic ion activity cannot yet be ascribed to specific biostates.