Active ion transport and beta-acdysone induced differentiation of Drosophila melanogaster imaginal discs cultured in vitro.
The theory that beta-ecdysone initiates developmental changes during insect metamorphosis by causing an increase in intranuclear levels of potassium, together with a concomitant decrease in sodium levels, has been investigated by two methods. First, imaginal discs from late third instar larvae have been cultured with 0-2 microng/ml of beta-ecdysone together with inhibitors of active ion transport. Non-specific inhibitors, which may have general effects on sulphydryl groups, such as iodoacetic acid, N-ethylmaleimide ethacrinic acid and furosemide, inhibit both eversion and differentiation at concentrations of from 10(-3) M to 2 X 10(-3) M. Ouabain, the only specific inhibitor of the active transport of Na+ and K+ across membranes, had no effect on development even at a concentration of 10(-2) M. Second, a medium containing raised levels of K+, and reduced concentrations of Na+, neither initiated disc development in the absence of beta-ecdysone, nor stimulated development induced by suboptimal levels (0-02 microng/ml) of beta-ecdysone, either in the presence or absence of ouabain. These results suggest that beta-ecdysone induced morphogenesis is not dependent upon Na+ and K+ concentrations, or on the activity of an ouabain-sensitive ion pump.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D004331:Drosophila melanogaster / Q000196:embryology*; D004440:Ecdysone / Q000494:pharmacology*; D005121:Extremities / Q000187:drug effects / Q000196:embryology; D066298:In Vitro Techniques; D009024:Morphogenesis / Q000187:drug effects; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D014921:Wings, Animal / Q000187:drug effects / Q000196:embryology
D004440:Ecdysone; D012964:Sodium; D011188:Potassium