title: The effects of sodium, potassium and ATP on a developmental puff sequence in Drosophila salivary glands in vitro.
abstract: Salivary glands of late third instar larvae of Drosophila melanogaster were isolated at a developmental stage when the release of ecdysone had already taken place. They were then incubated in a chemically defined medium. An ecdysone-dependent developmental puff sequence was measured in vitro and influenced by adding various substances or by changing iso-osmotically the sodium or potassium content of the medium. Trinactin, valinomycin N-ethylmaleimide and KCN blocked the puff sequence, i.e. the regression of the early and the induction of the late ecdysone-dependent puffs probably by increasing the Na+ influx and depleting the ATP content of the cell. A medium that contained Na+ as the only monovalent cation decreased the size of the late ecdysone-dependent puffs and increased the size of other puffs, such as 50 CD. Addition of tetrodotoxin to the normal medium had the opposite effect, i.e., it increased 63 E and inhibited 50 CD. Na+ free medium, inhibition of K+ flux by tetraethylammonium chloride, and application of ouabain did not considerably influence the size of the puffs measured. It is concluded from these results that Na+ in particular has an inhibitory effect on the induction of late ecdysone-dependent puffs. Na+ (and perhaps also K+) may act by modulating the effect of proteins that are involved in gene control mechanisms.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000031:analogs & derivatives / Q000494:pharmacology; D002875:Chromosomes / Q000187:drug effects*; D003486:Cyanides / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004331:Drosophila melanogaster; D004440:Ecdysone / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D007814:Larva; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology*; D012469:Salivary Glands / Q000648:ultrastructure; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D003486:Cyanides; D013757:Tetraethylammonium Compounds; D014634:Valinomycin; D004440:Ecdysone; D013779:Tetrodotoxin; D010042:Ouabain; D000255:Adenosine Triphosphate; D004247:DNA; D012964:Sodium; D005033:Ethylmaleimide; D011188:Potassium