Influence of Thyroxine on Different Ion-Dependent ATPase Activities in Fat Body of Tasar Silkworm,Antheraea mylittaD.

Abstract

The activities of Na+-K+-, Ca2+-, and Mg2+-ATPase of tasar silkworm,Antheraea mylittaD. fat body were investigated from fifth larval stage to adult emergence after injection of various doses (0.5, 1.0, 2.0, and 5.0 μg/g) of mammalian thyroxine (T4) to 1-hr-old fifth instar larvae. In normal silkworms, both sexes exhibited maximum enzyme activity before spinning (Day 12). Na+-K+-, Ca2+-, and Mg2+-ATPase activities in fat body of silkworms markedly declined after pupation and more so on the 1-day-old adults. All doses of thyroxine treated on fifth instar larvae significantly altered ATPase activity in the larval, pupal, and adult stages in both sexes. ATPase activity was not altered by lower dose of T4 (0.5 μg/g) in 2-day-old fifth stage larvae, while the higher dose (5.0 μg/g) surprisingly caused a reduction in ATPase activity during the different developmental stages. The fat body ATPases were influenced by thyroxine in all the stages of silkworm in a dose-dependent manner. Our results thus indicate that thyroxine has a controlling influence on the ATPase system in silkworm fat body.