Stimulated fluid secretion is sodium dependent in the Malpighian tubules of Locusta migratoria

P. J. Morgan*, W. Mordue

*Corresponding author for this work

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The ionic dependencies of stimulated and unstimulated Locusta tubules have been studied. K+, Na+, Cl- are essential to both basal and stimulated secretion. K+ is secreted against a concentration gradient in unstimulated tubules. In response to diuretic hormone or cAMP application, there is a dramatic influx of K+ into the lumen. A high level of Na+ and Cl- in the bathing medium is required to allow maximal fluid secretion. The tubules show an apparent impermeability to Na+; its concentration in the secreted fluid is always much less than in the bathing medium. If Na+ is omitted from the medium and excess K+ added (80 mM K), then although basal secretion occurs (2.5 nl/min), the tubules fail to respond to stimulation. Clearly Na+ has an important indirect role to play in stimulated fluid secretion.

Original languageEnglish
Pages (from-to)271-279
Number of pages9
JournalJournal of Insect Physiology
Issue number4
Publication statusPublished - 1 Jan 1981


ASJC Scopus subject areas

  • Physiology
  • Insect Science

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