Thyroxine influence on different ion-specific adenosine triphosphatase activities in fat body of Bombyx mori during development.

摘要

The effects of thyroxine on the activity of different ATPases (Na+-K+, Ca2+, and Mg2+) in fat body cells of the silkworm, Bombyx mori, were investigated during different development stages. In both sexes the maximum enzyme activity was observed in the fat body cells of day 7 last-instar larvae (the day before spinning). Na+-K+, Ca2+-, and Mg2+-ATPase activity in the fat body markedly declined after pupation and continued to decrease in day 1 adults. Injection of thyroxine (T4) at concentrations of1.0 and 2.0μg/g during the fifth-instar significantly elevated all ATPase activities in the larval, pupal, and adult stages in both sexes. At a concentration of 0.5μg/g, T4 had no effect on day 2 fifth-instar larvae, although it increased the ATPase activity of the other stages investigated. A higher concentration (3.0μg/g) caused a significant reduction in enzyme activity in all stages with the exception of day 2 fifth-instar larvae. Thus, the repression of enzyme activity with the higher concentration and the elevation of enzyme activity with the lower concentration established the biphasic nature of T4 action on the ATPase system in fat body cells of B. mori.