title: X-ray microanalysis of Rb+ entry into cricket Malpighian tubule cells via putative K+ channels.
abstract: Elemental imaging by X-ray microanalysis of fully frozen-hydrated samples shows that when Malpighian tubules of the black field cricket (Teleogryllus oceanicus L.) are incubated in saline in which Rb(+) has been substituted for K(+), Rb(+) replaces much of the cellular K(+) in the main segment of control Malpighian tubules and this is prevented by incubation in saline containing Ba(2+), a non-selective K(+) channel blocker. Similarly the amount of cellular K(+) is greatly reduced when tubules incubated in normal, i.e. K(+) containing, saline are exposed to Ba(2+). By considering the amounts of cellular K and Rb remaining in the main segments of tubules incubated in either K(+) containing saline or Rb(+) containing saline after Ba(+) treatment, it is suggested that: (a) a major part (56%) of cellular K(+) enters by Ba(2+) sensitive K(+) channels and that Rb(+) can also enter by this route; (b) a smaller fraction (26%) of cellular K(+) enters by a previously proposed Na(+)/K(+)/2Cl(-) co-transporter, which can also transport Rb(+); (c) a previously proposed Na(+)/K(+)-ATPase is responsible for maintaining a K(+) pool (18%) in the tubule cells that is not exchangeable by Rb(+); and (d) entry by this Na(+)/K(+)-ATPase is not available to Rb(+).
authors.affiliation: Department of Zoology and Analytical Electron Microscopy Laboratory, Faculty of Science, Technology and Engineering, La Trobe University, Melbourne, VIC 3086, Australia. A.Marshall@latrobe.edu.au
authors.forename: Alan T
authors.initials: AT
authors.lastname: Marshall
authors.forename: Peta L
authors.initials: PL
authors.lastname: Clode
mesh_terms: D000818:Animals; D001464:Barium / Q000378:metabolism; D001692:Biological Transport / Q000502:physiology; D004577:Electron Probe Microanalysis / Q000379:methods*; D006135:Gryllidae / Q000033:anatomy & histology / Q000378:metabolism; D008297:Male; D008317:Malpighian Tubules / Q000166:cytology / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*; D012413:Rubidium / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D026902:Potassium Channel Blockers; D015221:Potassium Channels; D028021:Sodium-Potassium-Chloride Symporters; D001464:Barium; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium