Induction of subcellular malic dehydrogenase activity in fat body cells of diapausing pupae of wild tasar silkworm Antheraea mylitta Drury (Lepidoptera : Saturniidae) by 17-beta estradiol

摘要

For elucidation of vertebrate estrogen-induced responsiveness of fat body cells of insects, various doses (0.5, 1.0, 5.0, 10 and 50 mu g) of 17-beta estradiol (E-2) were injected thrice, at 5 day intervals, to 130-day-old diapausing pupae of Antheraea mylitta and the changes in cytosolic NADP(+)-dependent (cMDH, EC 1.1.1.40) and mitochondrial NAD(+)-dependent (mMDH, EC 1.1.1.37) malic enzyme activity together with protein content of the subcellular fractions was determined. NADP(+)-linked cMDH activity decreased in both the sexes at the doses of 10 and 50 mu g of estrogen (E-2) per pupa. Lower doses of E-2 (0.5-5 mu g) also showed a trend in reduction of specific activity of the enzyme although the data was not found to be significant statistically. On the contrary, specific activity of NAD(+)-linked mMDH was enhanced with all the doses of estrogen used so far in both male and female insects. Protein content in tissue fractions of fat body cells of male and female pupae was elevated with all the doses of injected E-2 when compared to control, In general, females contained more protein in both the tissue fractions than their male counterparts while in case of malic enzyme activity it was found to be just the reverse. Hence, the activity of NADP(+) cMDH and NAD(+) mMDH in fat body cells and its responsiveness to the biologically active hormone estrogen in tasar silkworm has been documented as has been found in B. mori and other invertebrates. The steroid hormone effect in diapause regulatory mechanism is also established. [References: 45]