title: Intracellular storage of sodium and magnesium in Drosophila Malpighian tubules. X-ray microanalysis of native cryosections.
abstract: Using electron probe X-ray microanalysis after cryofixation, cryosectioning and freeze-drying we investigated the content of electron-dark vacuoles in the intermediate cell region of the proximal segment of Malpighian tubules in Drosophila larvae. According to this method these vacuoles store sodium and magnesium in a high correlation (r = 0.98) of 5:1 ratio. Phosphorus, potassium and sulfur are also stored. In the intermediate groundplasm surrounding the vacuoles the element content is different from that in the vacuoles. The significance of vacuolar sodium and magnesium storage for the ionic metabolism is unknown. In addition to Na, Mg, P, K and S the vacuoles also contain 3-OH-kynurenine and other fluorochromes. With the pyroantimonate technique intravacuolar precipitates were demonstrated. X-ray microanalysis of the precipitates revealed sodium and calcium, although following cryofixation calcium was not detectable in the vacuoles by X-ray analysis.
authors.affiliation: Institut für Allgemeine und Spezielle Zoologie, Justus-Liebig-Universität, Deutschland.
authors.forename: A
authors.initials: A
authors.lastname: Wessing
authors.forename: K
authors.initials: K
authors.lastname: Zierold
authors.forename: D
authors.initials: D
authors.lastname: Schäfer
mesh_terms: D000818:Animals; D000965:Antimony / Q000032:analysis; D002118:Calcium / Q000032:analysis / Q000378:metabolism; D002988:Cloaca / Q000378:metabolism*; D004330:Drosophila / Q000378:metabolism*; D004577:Electron Probe Microanalysis / Q000379:methods; D005615:Freezing; D008274:Magnesium / Q000032:analysis / Q000378:metabolism*; D008317:Malpighian Tubules / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D011309:Preservation, Biological / Q000379:methods; D012964:Sodium / Q000032:analysis / Q000378:metabolism*; D014617:Vacuoles / Q000032:analysis / Q000648:ultrastructure
chemical_list: C009133:pyroantimonate; D000965:Antimony; D012964:Sodium; D008274:Magnesium; D002118:Calcium