TRANSESTERIFICATION OF JUVENILE-HORMONE OCCURS IN-VIVO IN LOCUST WHENINJECTED IN ALCOHOLIC SOLVENTS

Catabolism of juvenile hormone was studied in vivo in the African locu st by injection of the labelled natural enantiomer (10R) (12-H-3) JH-I II. Due to the poor solubility of JH in aqueous solution, it was injec ted in a water-miscible solvent. Ethanol was chosen for its apparently low toxicity towards the locust. In these experimental conditions, re verse phase liquid chromatography procedure (RP-HPLC) coupled with on line radiodetection, revealed an apolar metabolite of JH-III. This com pound was found both in adult females and in fifth stadium larvae. We demonstrate that this metabolite resulted from substitution of the car boxyl methyl group of JH-III by some hydrophobic moiety. This compound co-migrates in our RP-HPLC system with the JH analog epoxy-ethyl farn esoate (JH-III ethyl ester) obtained by KCN-catalysed transesterificat ion of JH-III in ethanol. Both JH-III ethyl ester of chemical origin a nd biological compounds extracted from locusts give the same spectra w hen analyzed by gas chromatography-mass spectroscopy (GC-MS). Transest erification of JH-III was not observed with locust tissues incubated i n vitro but occurred in vivo even if JH was injected in other alcoholi c solvents such as propanol. Our data suggest that transesterification of JH-III occurred in vivo and underline the role of injecting solven t in in vivo studies.