Mechanism of branchial apical silver uptake by rainbow trout is via the proton-coupled Na+ channel

Nicolas R. Bury, Chris M. Wood

Research output: Contribution to journalArticlepeer-review

160 Scopus citations

Abstract

The branchial uptake mechanism of the nonessential heavy metal silver from very dilute media by the gills of freshwater rainbow trout was investigated. At concentrations >36 nM AgNO3, silver rapidly entered the gills, reaching a peak at 1 h, after which time there was a steady decline in gill silver concentration and a resulting increase in body silver accumulation. Below 36 nM AgNO3, there was only a very gradual increase in gill and body silver concentration over the 48-h exposure period. Increasing water sodium concentration ([Na+];0.05 to 21 mM) significantly reduced silver uptake, although, in contrast, increasing ambient [Ca2+] or [K+] up to 10 mM did not reduce silver uptake. Kinetic analysis of silver uptake at varying [Na+] showed a significant decrease in maximal silver transport capacity (173 ± 34 pmol · g-1. h-1 at 0.1 mM [Na+] compared with 35 ± 9 at 13 mM [Na+]) and only a slight decrease in the affinity for silver transport (Km;55 ± 27 nM at 0.1 mM [Na+] compared with 91 ± 47 nM at 13 mM [Na+] Phenamil (a specific blocker of Na+ channels), at a concentration of 100 μM, blocked Na+ uptake by 78% of control values (58% after washout), and bafilomycin A1 (a specific blocker of V-type ATPase), at a concentration of 2 μM, inhibited Na+ uptake by 57% of control values, demonstrating the presence of a proton-coupled Na+ channel in the apical membrane of the gills. Phenamil (after washout) and bafilomycin A1 also blocked silver uptake by 62 and 79% of control values, respectively, indicating that Ag+ is able to enter the apical membrane via the proton-coupled Na+ channel.

Original languageEnglish (US)
Pages (from-to)R1385-R1391
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume277
Issue number5 46-5
StatePublished - Nov 1 1999

Keywords

  • Bafilomycin A
  • Phenamil
  • Silver transport
  • Sodium channel
  • Teleost

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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