Effect of methoprene and 20-hydroxyecdysone on vitellogenin production in cultured fat bodies and backless explants from unfed female Dermacentor variabilis.

The effect of 20-hydroxyecdysone (20HE) and the juvenile hormone analogue methoprene (JHA) on vitellogenin (Vg) production in fat body organ cultures and backless explants of unfed female Dermacentor variabilis was measured. An indirect double antibody enzyme linked immunosorbent assay (ELISA) was developed using a monoclonal antibody that recognized a 98 kDa subunit of Vg and a Vg specific polyclonal antibody made against vitellin (Vn). Peak Vg titers in culture medium from fat body cultures treated with 0.1 &mgr;M 20HE or 1 &mgr;M 20HE were 24 ng/ml and 20 ng/ml respectively. In culture medium from backless explants treated with 0.1 &mgr;M 20HE or 1 &mgr;M 20HE, peak Vg titers were 36 ng/ml and 26 ng/ml, respectively. JHA produced only a slight increase in Vg titers that was statistically different from Vg titers produced by 20HE but was not statistically different from hormone-free controls. These results support the conclusion that Vg production in fat body trophocytes of D. variabilis is regulated by 20HE.