Figure 1. Diminution of the ESR signals of hydroxyl radicals by steroid. ESR signal of tyrosine radical was measured (Standard). A: Effect of 1mM steroid on ESR signals of hydroxyl radicals. B: Effect of 0.1, 0.3, 0.5 mM E2 and 2-OHE2 on ESR signals of hydroxyl radicals. The ESR setting was as follows: microwave power, 10 mW; modulation frequency, 100 kHz; modulation field, 0.1 G; receiver gain, 1000 and time constant, 0.3 s.