Metabolism of Δ0‐, Δ5‐, and Δ7‐Sterols by Larvae of Heliothis zea

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Abstract
Heliothis zea was reared on artificial diets containing Δ5‐sterols (cholesterol, campesterol, or sitosterol), Δ7‐sterols (lathosterol, epifungisterol, or spinasterol), or Δ0‐sterols (cholestanol, epicoprostanol, campestanol, or sitostanol) in order to determine how different dietary sterols affect the type of sterols present in the tissues of the late‐sixth‐instar larva. Although all of the dietary sterols (except epicoprostanol) supported the growth of the larvae, not all of the sterols were metabolized to the same end products. In each case, at least 80% of the sterols in the tissues of the larvae retained the same nucleus as that of the dietary sterol, indicating that H. zea carries out very little metabolism of ring B of Δ5‐, Δ7‐, and Δ0‐sterols. The larvae dealkylated the Δ5‐, Δ7‐, and Δ0‐alkylsterols to 24‐desalkylsterols, but a greater percentage of the Δ5‐alkylsterols were metabolized in this manner. The sterols present as free sterols in the larva were also present as esterifed sterols which accounted for 2–4% of the total sterols. Therefore, the sterol composition of the tissues of H. zea can be altered by varying the dietary sterols.