Studies on the Sterol of Bombyx mori L. : III Fate and Distribution of 4-¹⁴C-Cholesterol in the Silkworm

Abstract

The present study was carried out to elucidate a contribution of the pupal brain to sterol metabolism, observing the fate and the distribution of 4-^<14&&t;C-cholesterol in both normal and dauer pupae of the silkworm, Bombyx mori. After the injection of labelled cholesterol into the normal and the dauer pupae, the blood, several tissues, and remainder were dissected out from these pupae on 1 day after injection, 7 days and 1 day before emergence. Methanol extract was refluxed with ether, following each sample's extraction with methanol. The radioactivity of both the sterol ester and the free sterol fractions separated from the ether extract was counted. The incorporation of the labelled cholesterol into several tissues and the blood did not show any remarkable difference beween the normal and the dauer pupae. In the former, however, a large amount of cholesterol was demonstrated as ester form, while in the latter, free sterol was observed. Furthermore, the rate of esterification in dauer pupa sterol was slower than that of normal pupa, suggesting that unknown factor originating from brain had an intimate relation to sterol metabolism.