Tissue-Specific Incorporation of Azadirachtin in the Malpighian Tubules of Locus ta migratoria

The retent ion, tissue distr ibut ion, and localization of [22,23-H2 ]dihydroazadirachtin A was investigated in the female locust, Locusta migratoria. A constant quantity of 0.4 to 0.5 pg of dihydroazadiracht in A per gram body weight is recovered in the unchanged fo rm 5 days after in ject ion of any of the physiologically effective doses in the range of 1.5 to 3.0 pg/g. Malp ighian tubules account for 73.7% of the amount of dihydroazadirachtin A which is retained in the whole body. I n the Malp igh ian tubules it is localized in the basal and inner regions. I t is inferred f rom these results, that dihydroazadirachtin A acts in its unchanged form through a high-aff in i ty binding to organ-specific membrane receptors.