METABOLISM OF [H-3] ECDYSONE IN EMBRYOS AND LARVAE OF THE TICK ORNITHODOROS-MOUBATA

The fate of [H-3]-ecdysone ([H-3]-E) was investigated in hanging drop cultures of embryos and larvae of the tick Ornithodoros moubata using HPLC. The hormone was metabolized more slowly during described periods of increasing endogenous ecdysteroid (ES) titers than during periods of low titers except for young embryos. Three different classes of met abolites were produced: 1) apolar products (AP) corresponding to C-22 fatty acid ester conjugates of E and, in some cases, of 20-hydroxyecdy sone (20E), 2) unidentified polar products (PP) more polar than E, one peak of which had the same retention times as 20,26-dihydroxyecdysone , and finally, 3) 20E verified by comigration of cold standards on RP- 18 and silica columns. Hydroxylation of E to 20E first became evident in cultures of 2 day old embryos and was present in all cultures of ol der animals. Highest production of free 20E occurred during increasing endogenous ES titers in embryos and during the ES peak in larvae. Con jugation of E to AP occurred in all stages investigated, but was more pronounced during periods of low endogenous ES titers, and may corresp ond to a detoxification mechanism. In contrast, PP were produced durin g high 20E production in embryos and during periods of high and decrea sing endogenous titers in larvae.