. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INACTIVATION OF ECDYSONES 331 injected into mature larvae, 80% of activity disappeared in 2 hours (Karlson and Bode, 1969). In similar experiments performed on ligatured abdomens, the half- inactivation time was 3 hours (Shaaya, 1969). In additional studies of C. crythroccphala, Karlson and Bode (1969) extracted from larval fat-body a soluble enzyme system capable of inactivating a-ecdysone in vitro. The titer of this system was shown to undergo large and systematic changes during successive phases of metamorphosis. In exper
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INACTIVATION OF ECDYSONES 331 injected into mature larvae, 80% of activity disappeared in 2 hours (Karlson and Bode, 1969). In similar experiments performed on ligatured abdomens, the half- inactivation time was 3 hours (Shaaya, 1969). In additional studies of C. crythroccphala, Karlson and Bode (1969) extracted from larval fat-body a soluble enzyme system capable of inactivating a-ecdysone in vitro. The titer of this system was shown to undergo large and systematic changes during successive phases of metamorphosis. In experiments performed on Calliphora vicina, King and Siddall (1969) ob- served a much slower inactivation of a-ecdysone than noted in the above mentioned studies of C. ery throe cphala and .S. peregrina. For example, when tritiated a-ecdysone was injected into mature larvae, no less than 25% of the tritium label was recovered 12-24 hours later in two materials identified as a- and /3-ecdysones. Evidently, the dynamics of ecdysone metabolism can show substantal differences even among closely related species. In the present investigation a relatively slow inactivation of a-ecdysone was evident in experiments performed on the two species of silkworm pupae. As illustrated in Figure 3, the half-inactivation time was about 6 hours, and 15-20% of initial activity remained after 24 hours. According to King and Siddall (1969), the first step in the metabolism of a-ecdysone is hydroxylation at C-20 to form /3-ecdysone; the experiments in ques- tion made use of tritiated a-ecdysone and were performed on Calliphora vicina and two species of crustaceans. Subsequently, this finding has been confirmed by Cherbas and Cherbas (1970) in detailed studies of the metabolism of tritiated a-ecdysone by diapausing pupae of the silkworm, Antheraea polyphemus. These investigators report, moreover, that the further metabolism of /3-ecdysone is accom- 100 8 Cyasterone. 0 8 16 20 24 28 32 Hours After Injection
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
