Investigation of the endocrine system in extended longevity lines of Drosophila melanogaster

There is a complete absence of information about the endocrinology of Drosophila melanogaster in relation to genetic-based differential longevity in this model species. In the present study, aspects of the endocrine system of D. melanogaster were investigated in selected and control lines characterized by relative differences in life span. By using extracts from whole bodies, steroid hormone (ecdysteroid) titers were determined by radioimmunoassay in all replicate selected and control lines on the first and fourth day of adult life. The results suggest that ecdysteroid titers were relatively reduced on the first day post-eclosion in females from the long-lived lines, but this difference was not present on the fourth day posteclosion. The reduction in early-age ecdysteroid titers in long-lived females might be related to the decrease in early-age fecundity in the selected lines. There was no difference between line types in male ecdysteroid titers on either day post-eclosion. Two classes of enzymes that act on juvenile hormone were also investigated in the present study. Esterase and epoxide hydrolase activity on juvenile hormone was assessed in females in all replicate selected and control lines at approximately 12 h or 4 days post-eclosion. There was no difference between selected and control lines in the specific activity of either class of enzymes that metabolize juvenile hormone.