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 Google Scholar Google Scholar Articles by GOSS, G. G. Articles by WOOD, C. M. Search for Related Content PubMed Articles by GOSS, G. G. Articles by WOOD, C. M.

Journal of Experimental Biology 152,549-571 (1990)
Published by Company of Biologists 1990

Na⁺ and Cl^- Uptake Kinetics, Diffusive Effluxes and Acidic Equivalent Fluxes Across the Gills of Rainbow Trout : II. Responses to Bicarbonate Infusion

GREG G. GOSS ¹ and CHRIS M. WOOD ²

¹ Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1; Department of Biology, University of Ottawa, 30 George Glinski Pr., Ottawa, Ontario, Canada K1N 6N5
² Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1

Adult rainbow trout fitted with arterial and bladder catheters were chronically infused with either bicarbonate (as NaHCO₃) or NaCl for 19 h at approximately 410 µequiv kg^-1h^-1. NaHCO₃ infusion produced a pure exogenous metabolic alkalosis of approximately 0.35 pH units accompanied by a decrease in plasma [Cl^-] but no change in plasma [Na⁺]. Alkalosis stimulated Cl^- influx and inhibited Na⁺ influx (measured at 10-16 h infusion), resulting in a negative Na⁺ balance, a positive Cl^- balance and a large net basic equivalent excretion (=acidic equivalent uptake) across the gills. The latter was approximately equal to the rate of HCO₃^- loading. The kidney accounted for approximately 13% of the acid-base compensation.

Kinetic analysis revealed that reductions in J_in^Na were accomplished by increases in K_m^Na (463 µequiv l^-1; NaHCO₃-infused vs 276 µequiv l^-1; NaCl-infused) and large decreases in J_max^Na (262 µequiv kg^-1 h^-1 vs 689 µequiv kg^-1 h^-1) while stimulation of J_max^Cl was accomplished by large increases in J_max^Cl only (674 µequiv kg^-1 h^-1 vs 360 µequiv kg^-1 h^-1). Thus, J_max can be increased or decreased in response to acid-base disturbance, but K_m can only be increased; the Na⁺ and Cl^- carriers operate close to maximum affinity under control conditions. Basic equivalent excretion was described by a virtually identical kinetic curve to that of the Cl^- uptake. NaHCO₃ infusion also induced a differential diffusive efflux of Na⁺ over Cl^- which could account for up to 35% of the acid-base compensation during alkalosis.

Key words: hyperoxia, uptake kinetics, K_m, J_max, efflux, Michaelis-Menten

Accepted on May 15, 1990