Distribution of tritiated ecdysone in salivary glands and other tissues ofRhynchosciara andChironomus larvae an autoradiographic study.

The distribution of tritium-labelled ecdysone in salivary glands ofChironomus tentans and different tissues ofRhynchosciara spec, has been studied, following in vivo incubations and either of two modified ethanol-acetic acid fixation techniques. The results of autoradiographic analysis show maximum label over the cytoplasm or evenly labelled cytoplasm and nuclei, within a wide range of incubation times. Indications of distinct localization at chromosomal loci are not conclusive. There is a remarkably high amount of radioactivity in the lumen of the anterior intestine as soon as six minutes after hormone injection. The limitations of histoautoradiographic studies in attempts to localize the cellular receptor of ecdysone are discussed.