Studies on the Sterol of Bombyx mori L. : VI. Incorporation of 2-14C-Mevalonic Acid into Silkworm Lipids

Abstract

The present study has been carried out to follow the incorporation of 2¹⁴C-mevalonic acid into sterol in silkworm pupa and larva. An awueous solution of 2-¹⁴C-mevalonic acid lactone was injected into the 5th instar larvae of 72 hour-old and into pupae of 0 day- and 5 day-old. The incorporation of 2-¹⁴C-mevalonic acid into unsaponifiable fraction increased from 2.65 to 6.75 % following the progress of stage from larva to pupa and that into the sterol fraction from 0.002 to 0.003%. Thus, it is concluded from trace incorporation in the latter that the silkworm cannot synthesize sterol from acetate via mevalonic acid, and that phytosterols in the silkworm are derived from dietary phytosterols, and cholesterol is converted from dietary phytosterols.