Biosynthesis of ecdysones in isolated prothoracic glands and oenocytes of Tenebrio molitor in vitro

Isolated prothoracic glands from Tenebrio larvae synthesize in vitro α-ecdysone, but not β-ecdysone from 4-¹⁴C-cholesterol. Isolated abdominal oenocytes from the larvae synthesize mainly β-ecdysone, but only little α-ecdysone. When prothoracic glands and oenocytes are cultured together, the α-ecdysone derived from the prothoracic glands is oxidized by the oenocytes to β-ecdysone. The newly synthesized hormones are not stored in the cells, but are secreted into the medium if sufficient amounts of non-labelled hormones are present. If no unlabelled hormones are added to the culture medium, the newly formed hormones are converted to a large extent into polar conjugates.