QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by EVANS, D. H. Articles by MORE, K. J. Search for Related Content PubMed Articles by EVANS, D. H. Articles by MORE, K. J.

Journal of Experimental Biology 138,375-397 (1988)
Published by Company of Biologists 1988

Modes of Ammonia Transport Across the Gill Epithelium of the Dogfish Pup (Squalus Acanthias)

DAVID H. EVANS ¹ and KANE J. MORE ²

¹ Department of Zoology, University of Florida, Gainesville, FL 32611, USA and Mount Desert Island Biological Laboratory Salsbury Cove, ME 04672, USA
² Department of Zoology, University of Florida Gainesville, FL 32611, USA and Mount Desert Island Biological Laboratory Salsbury Cove, ME 04672, USA

The modes of ammonia transport across the gill epithelium of the dogfish pup (Squalus acanthias) were investigated using an isolated, perfused head preparation. During perfusion for 2–3 h there was no obvious oedema of gill lamellae, the head was haemodynamically responsive to near-in-vivo concentrations of adrenaline, and the transepithelial potential was +1.9mV (perfusate relative to irrigate) and was unaffected by any of the potential inhibitors used in these tudies. The rate of ammonia efflux was somewhat above in vivo levels, was not due to structural leaks (which averaged less than 1%), declined by 17 % during a second, 20-min efflux period, but was stable during a third efflux period. Addition of bumetanide to the perfusate inhibited ammonia efflux by 17 % compared with the control, but subsequent addition of ouabain had no effect. Amiloride added to the irrigate in the presence of ouabain in the perfusate had no effect on ammonia efflux. Ammonia efflux was stimulated by specific increases in perfusate P_NH3 much more (1100 times) than by specific increases in perfusate NH₄⁺ concentrations. Given a pK of ammonia of 9.75, we calculate that 6% of the total ammonia efflux is via ionic diffusion of NH₄⁺, 77% via non-ionic diffusion of NH₃, and 17 % via a bumetanide-sensitive Na⁺+NH₄⁺+2Cl^- cotransport system. Basolateral or apical Na⁺/NH₄⁺ exchange apparently is not involved in ammonia transport across this epithelium.

Key words: shark, Squalus acanthias, gill, ammonia

Accepted on April 14, 1988

This article has been cited by other articles:

				D. H. Evans, P. M. Piermarini, and K. P. Choe The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and Excretion of Nitrogenous Waste Physiol Rev, January 1, 2005; 85(1): 97 - 177. [Abstract] [Full Text] [PDF]

				S. P. Kelly and C. M. Wood The cultured branchial epithelium of the rainbow trout as a model for diffusive fluxes of ammonia across the fish gill J. Exp. Biol., January 12, 2001; 204(23): 4115 - 4124. [Abstract] [Full Text] [PDF]