RESUMO
Estradiol-17beta (E2) at the dose of 1 microg/g caused an increase in cell area, lumen area and the total (cell + lumen) area of posterior silk gland (PSG) in Bombyx mori indicating that exogenously applied estradiol-17beta has a regulatory influence on silk gland activity. A dose-dependent variation in trehalase activity of PSG was found on the 5th day after topical administration of estradiol on 1st and 2nd day of the fifth larval instar. Of all the doses of E2 used, 1 microg/g dose had maximum stimulatory effect on trehalase activity. Co-administration of each of a specific receptor antagonist for estradiol, the ICI-182780 and a protein biosynthetic blocker, cycloheximide with E2 suppressed the E2-induced increase in silk gland activity. The results suggest some specific metabolic action of E2 on silk gland and offer a promising way for future investigations regarding the physiological significance of vertebrate steroids in insects.