Changes in redox states of respiratory pigments recorded from the eyes of live blowflies exposed to light stimuli and hypoxia

Time courses of mitochondrial responses to illumination-induced physiological loads and to hypoxia, were recorded optically from eyes of blowflies Calliphora vicina chalky. We isolated changes in redox states of haems a(3), a, c, and b. Two types of responses to light stimulation were observed. Haems b and a(3) responded with transient oxidation and haems a and c with reduction. The same two groups emerged in response to anoxic exposure. The onset of reduction of haems a and c had virtually no latency, while haems a(3) and b exhibited a transient oxidation followed by reduction only after 10-20 s. The dependence of the steady-state reduction level on P-O2 produced the same groups. Haems a and c were significantly reduced at P-O2 levels around 10 kPa while with haems b and a(3) load-induced oxidation was only replaced by reduction below 2 kPa. We propose haems respond to physiological loads in accordance with their steady-state reduction, which in turn depends largely on barriers for electron transport imposed by the mitochondrial membrane potential. We also propose it may be possible to assess the values of tissue P-O2 and O-2 consumption by monitoring haems that are highly oxidized at rest such as haem a.