Paramagnetic changes in pulmonary tumors.

Electron spin resonance studies on healthy and tumorous human lung samples have been conducted in order to determine possible differences in free radical concentration and shaped of the spectra between the different sections of the lung. It could be shown that in healthy lung tissue the signal caused by the semidehydroascorbate (SDA) radical is not prominent because of the prevailing high partial oxygen pressure. On formation of a tumor, the spin concentration increases, possibly due to the higher metabolic rate; here, the SDA peak is also more pronounced which indicates alterations in the interaction between cell constituents and ascorbic acid. Within the tumor, the spin concentration is considerably reduced which is probably caused by a still higher concentration of ascorbic acid. Addition of ascorbic acid to the different lung specimens enhanced the just described effect while oxidizing substances, such as H2O2, reversed it.