© 1972 by The Society for Integrative and Comparative Biology
Studies on Hormone Recognition by Arthropod Target Tissues
Department of Biological Sciences, Northwestern University Evanston, Illinois 60201
Zoëcon Corporation Palo Alto, California 94304
Numerous experiments have implicated the crustacean hepatopancreas as a target of the molting hormone, and recent studies strongly suggest that ß-ecdysone is the crustacean molting hormone. For example ß-ecdysone can elicit molting in niter-molt crustaceans and stimulates the synthesis of protein and RNA in the hepatopancereas. When 3H-
-ecdysone is injected into premolt crayfish, it is efficiently excreted, but label can be detected in almost all tissues examined. To determine whether target tissues contain specific "receptor" molecules which distinguish those tissues that respond to molting hormone from those that do not, a series of in vivo and in vitro experiments were conducted utilizing Sephadex chtomatography and sucrose density gradient ultracentrifugation. These studies reveal the presence of two proteins in the cytosol fraction of the hepatopancreas that bind label from the 3H--ecdysone. These proteins have approximate molecular weights of 250,000 (11.3S) and 130,000 (6.35S), and the larger may be an aggregate of the smaller. Micro-chemical analysis demonstrated that the label associated with these proteins is no longer attributable to -ecdysone nor any ecdysone-like compound thus far described. Two alternate structures are described that may represent the metabolite bound to the protein, and it is suggested that the binding protein-metabolite complex may be the the active from of the molting hormone. Studies are also described dealing witha hemolymph lipoprotein in silkmoths that binds juvenile hormone and it is postulated that the water soluble hemolymph lipoprotein-juvenile hormone complex is the means by which the lipoidal juvenile hormone is transported in the aqueous hemolymph.