Distribution and metabolism of alpha-ecdysone in pupae of the silkworm antheraea polyphemus.

Abstract

1. The distribution of inulin, water, and α-ecdysone was studied in pupae of the silkworm Antheraea polyphemus. All three compounds reach equilibrium within two hours after injection.2. Inulin is restricted to the extracellular space, which amounts to 0.49 ml per g live weight.3. The ecdysone space is slightly larger than the water space. About 50% of the radioactivity derived from α-ecdysone remains in the blood for at least 36 hours.4. The other 50% is associated with cells in a form which cannot be removed by extensive washing of the intact tissues with saline.5. Transport of ecdysone to the tissues does not involve a rate-limiting carrier system that can be saturated by 10 µg α-ecdysone or 100 µg β-ecdysone.6. There is no evidence that ecdysone is accumulated by any one tissue or excretory organ.7. The metabolism of α-ecdysone was studied by thin layer chromatography of extracts of blood after injection of radioactive α-ecdysone. α-ecdysone is rapidly converted to β-ecdysone and the latter to several more polar metabolites.8. β-ecdysone either inhibits the conversion of α-ecdysone to β-ecdysone or is itself converted to α-ecdysone at a significant rate.