Gd3+-sensitive Na+ transport across the integument of Hirudo medicinalis.
Leeches Hirudo medicinalis were exposed to either artificial pond water (APW; 1 mM NaCl) or to high-salinity conditions (HS; 200 mM NaCl) for several days. The aim of the study was to assess whether transepithelial ion conductances in their dorsal integuments were affected by this long-term acclimation. In voltage-clamp experiments using Ussing-type chambers, the transepithelial potential V(T) was clamped to 0 mV, and amiloride-sensitive currents (I(ami)) and total Na(+) transport (I(Na)) were determined. Apical Ca(2+)-free conditions strongly increased I(ami) to a similar magnitude in both differently acclimated integuments. Apical application of the lanthanide gadolinium <0.1 mM decreased the short-circuit current (I(sc)). In contrast, higher concentrations up to 10 mM Gd(3+) upregulated I(sc) by an additional 90% in APW integuments and by an additional 300% in HS integuments. This Gd(3+) effect was due to a doubling of I(Na) in APW and a more than sixfold increase of I(Na) in HS integuments. In summary, the macroscopic electrophysiological variables, including I(Na), were generally not affected by long-term exposure to high salinity. However, the presence of Gd(3+)-sensitive Na(+) conductances or regulating structures were greatly upregulated during HS acclimation.
Schnizler
Mikael
M
Institut für Tierphysiologie der Justus-Liebig-Universität Giessen, Giessen, Germany. mikael.k.schnizler@physzool.bio.uni-giessen.de
Clauss
Wolfgang
W
D000064:Acclimatization; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004594:Electrophysiology; D005682:Gadolinium / Q000494:pharmacology*; D034582:Integumentary System / Q000502:physiology*; D017136:Ion Transport / Q000187:drug effects*; D007865:Leeches / Q000187:drug effects* / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism
D015222:Sodium Channels; D012964:Sodium; D005682:Gadolinium; D002118:Calcium