Release of a juvenile hormone binding protein by fat body of the Indian meal moth, Plodia interpunctella,in vitro

When fat body of fifth instar larvae of Plodia interpunctella was cultured in vitro in a chemically defined medium, the tissue released a low mol. wt protein (FBBP) that binds juvenile hormone (JH). This FBBP has the same mol. wt, estimated by gel permeation chromatography, as the haemolymph JH binding protein. Furthermore, the FBBP protected JH from degradation by general esterases isolated from the haemolymph. Treatment of fat body with cycloheximide inhibited incorporation of ¹⁴C] leucine into the FBBP protein fraction and reduced the amount of FBBP released into the medium. We conclude that one source of the JH binding protein found in the haemolymph is the fat body.