SUPEROXIDE ANION GENERATION BY PACIFIC OYSTER (CRASSOSTREA-GIGAS) HEMOCYTES - IDENTIFICATION BY ELECTRON-SPIN-RESONANCE SPIN-TRAPPING AND CHEMILUMINESCENCE ANALYSIS

1. The generation of a superoxide anion (O2.-) by hemocytes of the Pacific oyster, Crassostrea gigas, was investigated by using electron spin resonance spin trapping with the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and by the chemiluminescence method. 2. Oyster hemocytes released O2.- on stimulation with phorbol myristate acetate as revealed by both methods. 3. A great difference was found in O2.- -generating activity among three subpopulations of hemocytes, which were separated from each other by using Percoll density gradients. 4. Evidence obtained in our experiments suggests that a specific O2.- -forming system, which becomes functional upon adequate stimulation, exists in a specialized subpopulation of C. gigas hemocytes similar to the professional phagocytes in mammals.