DEVELOPMENT OF RESPIRATORY ACTIVITY AND OXIDATIVE PHOSPHORYLATION IN FLIGHT MUSCLE MITOCHONDRIA OF BLOWFLY LUCILIA CUPRINA

Adult development in Lucilia cuprina involves the formation of large numbers of thoracic mitochondria containing an extremely active system for the oxidation of α-glycerophosphate, which provides a convenient marker for studying their development. Mitochondrial fractions have been isolated at various stages of adult development of L. cuprina by density gradient centrifugation and the distributions of protein, α-glycerophosphate dehydrogenase, and oxidase in the gradients studied. Over the period of emergence there is an increase in the mean specific gravity of the mitochondrial population indicating a concentration of enzymic and non-enzymic (structural) protein. Initially the mitochondria accumulate mainly dehydrogenase protein; accumulation, incorporation, and organization of 'oxidase' protein is somewhat slower so that dehydrogenase cannot be fully expressed as oxidase. Over the period of emergence 'oxidase' protein is accumulated faster than dehydrogenase and the complexity of internal organization increases so that in post-emergent tissue the mature dense mitochondria can fully express dehydrogenase as oxidase. Thus development involves the asynchronous incorporation of enzymic and non-enzymic protein, the latter being laid down most rapidly over the period of emergence. Phosphorylation capacity develops synchronously with the oxidase. The respiratory chain is extremely sensitive to ADP and oligomycin before adult emergence. After emergence, although the mitochondria are still coupled, there is a marked decrease in respiratory control by ADP and a marked increase in control by Ca2+. The results are considered in relation to the development of flight muscle sarcosomes already described by Lennie and Birt and also in relation to the physiological changes which occur after emergence as the insect prepares for flight. © 1969.