Metabolic Control of Luminescence in Isolated Photophores of Porichthys - Effects of Glucose On Oxygen-consumption and Luminescence

1. Basal oxygen consumption of isolated photophores from Porichthys sp. at rest, i.e. without light emission, increased significantly from 0.101 +/- 0.021 nmol min-1 to 0.173 +/- 0.016 nmol min-1 in response to the addition of 5.5 mmol l-1 glucose. 2. 5.5 mmol l-1 glucose pretreatment modified the time course of the two phases of adrenaline-induced luminescence; an increase in oxygen consumption was observed during the fast phase of light production but a decrease occurred during the slow phase of luminescence. 3. Pretreatment of isolated photophores with 5.5 mmol l-1 glucose totally inhibited the light emission induced by 1 mmol l-1 potassium cyanide. With this treatment, the respiration rate decreased progressively and after 40 min reached a value not significantly different from zero. 4. Even after blockage of cellular respiration by cyanide, an increase in the rate of oxygen consumption was observed during the fast adrenaline-induced luminescence. 5. Glucose utilisation by glycolysis or by oxidative metabolism may provide energy to an inhibitory mechanism that maintains the photophores in a non-luminescent state. 6. We suggest that the oxygen consumed during the fast phase of adrenaline luminescence could represent the activity of an extramitochondrial oxidative pathway involved in the light reaction.