The mudskipper, Periophthalmodon schlosseri, actively transports NH4/+ against a concentration gradient

D. J. Randall, J. M. Wilson, K. W. Peng, T. W.K. Kok, S. S.L. Kuah, S. F. Chew, T. J. Lam, Y. K. Ip

Research output: Contribution to journalArticle

121 Scopus citations

Abstract

Periophthalmodon schlosseri can maintain ammonia excretion rates and low levels of ammonia in its tissues when exposed to 8 and 30 mM NH4Cl, but tissue ammonia levels rise when the fish is exposed to 100 mM NH4Cl in 50% seawater. Because the transepithelial potential is not high enough to maintain the NH4/+ concentration gradient between blood and water, ammonia excretion under such a condition would appear to be active. Branchial Na+- K+ATPase activity is very high and can be activated by physiological levels of NH4+ instead of K+. Ammonia excretion by the fish against a concentration gradient is inhibited by the addition of ouabain and amiloride to the external medium. It is concluded that Na+-K+-ATPase and an Na+/H+ exchanger may be involved in the active excretion of ammonia across the gills. This unique ability of P. schlosseri to actively excrete ammonia is related to the special structure of its gills and allows the fish to continue to excrete ammonia while air exposed or in its burrow.

Original languageEnglish (US)
Pages (from-to)R1562-R1567
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume277
Issue number6 46-6
DOIs
StatePublished - Dec 1999

Keywords

  • Amiloride
  • Ammonia
  • Na+-NH/-ATPase
  • Ouabain

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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