Swelling of mitochondria induced by juvenile hormone in larval salivary glands of Drosophila melanogaster.

Treatment of Drosophila larval salivary glands with juvenile hormone or its analogues leads to ultrastructural changes of mitochondria that mimic those seen after application of uncouplers of oxidative phosphorylation. This alteration of mitochondria, also known as swelling, is manifested in strong dilatation of their intercristae space. The mitochondrial response of salivary glands to juvenile hormone is restricted to collum cells that are known to be ultrastructurally and functionally different from transitional and corpus cells and may reflect their specialization in energy metabolism and water/ion balance. Morphological change of mitochondria and about a fivefold increase in cytochrome c oxidase activity in response to juvenile hormone appear to be a consequence of uncoupling of oxidative phosphorylation. We have noticed no significant difference of the responses in Methoprene, the juvenile hormone resistant mutant, suggesting that this action of juvenile hormone may be mediated via a mechanism different from that using nuclear transcription factors. The "uncoupling" effect is caused also by juvenile hormone analogues which are considered inactive in producing morphogenetic effects in Drosophila. Mitochondrial response is independent of transcription and translation, as revealed by the use of RNA and protein synthesis inhibitors. Given these data together, we reasoned that the protonophoric/uncoupling effect of juvenile hormone is a cell type specific nongenomic response to this lipophilic ligand and contrasts with widely accepted notions about nuclear action of juvenile hormone.