Effects of Perfusate HCO3− and Pco2 on Chloride Uptake in Perfused Gills of Rainbow Trout (Salmo gairdneri)

1984 ◽  
Vol 41 (12) ◽  
pp. 1768-1773 ◽  
Author(s):  
S. F. Perry ◽  
P. Payan ◽  
J. P. Girard
Keyword(s):  
Rainbow Trout ◽  
Carbonic Anhydrase ◽  
Chloride Transport ◽  
Salmo Gairdneri ◽  
Gill Epithelium ◽  
Major Pathway ◽  
Chloride Uptake ◽  
Transport Inhibitors ◽  
Initial Results ◽  
Stimulation Of

Experiments were conducted using a saline-perfused trout (Salmo gairdneri) head preparation in an attempt to determine the origin of HCO3− involved in gill apical Cl−/HCO3− exchange, the possibilities being plasma CO2 or HCO3−. Initial results showed that branchial Cl− influx was stimulated both by increased perfusate [HCO3−] and Pco2. Subsequent experiments employing the chloride transport inhibitors, SITS and thiocyanate, indicated that stimulation of Cl− influx by HCO3− probably was due to gill hemodynamic alterations and not to increased entry of HCO3− into the gill epithelium. We conclude that CO2 entry into the gill epithelium from plasma and its subsequent hydration to HCO3− and H+, by carbonic anhydrase, is a major pathway by which HCQ3− for Cl−/HCO3− exchange is generated.

scholarly journals The pattern of carbon dioxide excretion in the rainbow trout Salmo gairdneri

1978 ◽  
Vol 72 (1) ◽  
pp. 17-24
Author(s):  
M. S. Haswell ◽  
D. J. Randall
Keyword(s):  
Carbon Dioxide ◽  
Rainbow Trout ◽  
Carbonic Anhydrase ◽  
Severe Anaemia ◽  
Salmo Gairdneri ◽  
Gill Epithelium ◽  
Acid Base ◽  
Plasma Bicarbonate ◽  
O2 Delivery ◽  
Co2 Excretion

1. Patterns of carbon dioxide excretion were investigated in rainbow trout (Salmo gairdneri). 2. The loss of erythrocytic carbonic anhydrase caused by severe anaemia does not affect acid/base regulation or the ability of fish to excrete CO2. 3. Bicarbonate excretion across the saline-perfused gills of trout is significant even though residence time for the saline in the gills is only 1--3 s. CO2 excretion across these saline-perfused gills is blocked by the carbonic anhydrase inhibitor, diamox. 4. The excretion of CO2 in fish is via the movement of plasma bicarbonate into the gill epithelium where branchial carbonic anhydrase catalyses the production of CO2. Fish can adjust pH by regulating bicarbonate movement across the gills. 5. The erythrocytic carbonic anhydrase is not necessary for CO2 excretion in the gills but is involved in facilitating Bohr and Root shifts to augment O2 delivery in the tissues.

scholarly journals Carbonic anhydrase (acetazolamide-sensitive esterase) activity in the blood, gill and kidney of the thermally acclimated rainbow trout, Salmo gairdneri

1978 ◽  
Vol 73 (1) ◽  
pp. 15-27
Author(s):  
A. H. Houston ◽  
L. S. McCarty
Keyword(s):  
Rainbow Trout ◽  
Carbonic Anhydrase ◽  
Incubation Temperature ◽  
Carbonic Anhydrase Activity ◽  
Salmo Gairdneri ◽  
Plasma Sodium ◽  
Blood Levels ◽  
Acclimation Temperature ◽  
Chloride Uptake ◽  
Intimate Association

1. Gill, kidney and blood levels of acetazolamide-sensitive esterase (carbonic anhydrase) activity were estimated at acclimation temperature and at a common temperature (25 degrees C) in rainbow trout acclimated to 2, 10 and 18 degrees C. Plasma levels of sodium, potassium and chloride were also examined for possible acclimatory variations. 2. Plasma sodium and chloride levels, and the sodium:chloride ratio were unaffected by thermal acclimation; potassium concentrations were significantly elevated at 18 degrees C. 3. Significant, but modest changes in renal and branchial carbonic anhydrase activity were observed under physiologically realistic incubation temperature conditions. Blood carbonic anhydrase activity was sharply elevated at higher acclimation temperatures. 4. The data are discussed in relation to the hypothesis that carbonic anhydrase in this relatively stenothermal freshwater salmonid, through its intimate association with the coupled HCO-3/CL- and H+ +NH+4/Na+ exchange systems may provide for relatively thermostable basal rates of sodium and chloride uptake from the medium and recovery from urine. The renal, and more notably the branchial (Na+/K+)-stimulated ATPase systems, and erythrocytic carbonic anhydrase may then serve primarily as high-temperature amplifiers of sodium and chloride recruitment respectively.

Active Chloride Transport by the Gills of Rainbow Trout (Salmo Gairdneri)

1972 ◽  
Vol 56 (1) ◽  
pp. 263-272
Author(s):  
THEODORE H. KERSTETTER ◽  
LEONARD B. KIRSCHNER
Keyword(s):  
Chloride Transport ◽  
Gill Filament ◽  
Salmo Gairdneri ◽  
Apparent Effect ◽  
Chloride Uptake ◽  
Potassium Influx ◽  
The Mean ◽  
Kinetics Of ◽  
Trout Gill ◽  
Penetrating Cations

1. The kinetics of chloride transport by the irrigated trout gill have been studied. The transport system is saturable, and the half-saturation value is about 0.25mM. 2. Chloride uptake occurs equally well from solutions of non-penetrating cations and from NaCl solutions. The presence of potassium in the irrigating solution, however, significantly inhibits chloride uptake. 3. The trout gill is permeable to potassium, and there appears to be an active component to potassium influx. 4. Chloride transport is stimulated by injections of NaHCO3 and (NH4)HCO3. The carbonic anhydrase inhibitor, acetazolamide, has no apparent effect on chloride influx, and it is suggested that if a Cl-/HCO3- exchange exists in the trout gill, sufficient HCO3- can be supplied by the blood. 5. The mean intracellular potential (relative to the irrigating solution) of five gill filament cells was -32 mV. This indicates the presence of an energy barrier to chloride uptake at the outer membrane of the epithelium, and therefore it is postulated that an active step for chloride transport is located on this membrane.

Zinc Influx Across the Isolated, Perfused Head Preparation of the Rainbow Trout (Salmo gairdneri) in Hard and Soft Water

1988 ◽  
Vol 45 (12) ◽  
pp. 2206-2215 ◽  
Author(s):  
Douglas J. Spry ◽  
Chris M. Wood
Keyword(s):  
Steady State ◽  
Rainbow Trout ◽  
Hard Water ◽  
Soft Water ◽  
Chloride Cells ◽  
Salmo Gairdneri ◽  
First Order ◽  
Scanning Electron Micrography ◽  
Primary Substrate ◽  
Stimulation Of

At a waterborne [Zn] of 1.9 mg∙L−1 in hard water (~1 mmol Ca∙L−1), Zn influx across an isolated, saline-perfused head preparation of rainbow trout (Salmo gairdneri) was about 1.5 nmol∙kg−1∙h−1 through the lamellar pathway and about 1 nmol∙kg−1∙h−1 through the filamental route. Flux rates came rapidly to steady state in both pathways. Trout preexposed to artificial soft water (~0.05 mmol Ca∙L−1) for 5 d showed differential stimulation of flux rates to about 42 and 5 nmol Zn∙kg−1∙h−1 through the lamellar and filamental pathways, respectively. Under these conditions, steady-state fluxes across the lamellae did not occur until 15–20 min after the start of perfusion. Preparations from hardwater-acclimated trout tested in soft water gave typical hardwater fluxes showing that these changes in influx were not simply due to acute exposure of the gill surface to low waterborne [Ca]. Influxes in softwater trout, studied over [Zn] from 0.4 to 7.5 mg Zn∙L−1, revealed a saturable, first-order uptake with apparent Jmax and Km of 150 nequiv∙kg−1∙h−1 and 1.5 mg Zn∙L−1 (23 μmol∙L−1), respectively. Because the apparent Km is in the toxic range, Zn is clearly not the primary substrate. Scanning electron micrography revealed hypertrophy and increased apical exposure of chloride cells; this stimulation, coupled with the increase in Zn influx, suggests that chloride cells may be the site of entry of Zn across the gill.

scholarly journals Downstream pH Changes in Water Flowing Over the Gills of Rainbow Trout

1986 ◽  
Vol 126 (1) ◽  
pp. 499-512 ◽  
Author(s):  
PATRICIA WRIGHT ◽  
TOM HEMING ◽  
DAVID RANDALL
Keyword(s):  
Rainbow Trout ◽  
Carbonic Anhydrase ◽  
Control Fish ◽  
Salmo Gairdneri ◽  
Stopped Flow ◽  
Water Acidification ◽  
Interlamellar Water ◽  
Water Ph ◽  
Ph Stat ◽  
Control Water

We investigated the pH of interlamellar water of trout (Salmo gairdneri) by following changes in the downstream pH of expired water using a stopped-flow method. As water flowed over the gills of control fish, there was a significant decrease in water pH. Acetazolamide added to the water increased the CO2 disequilibrium, while carbonic anhydrase (CA) eliminated the CO2 disequilibrium relative to control water. Mucus excreted by the fish was found to contain CA activity by the pH-stat technique. We conclude water acidification is due to the conversion of excreted CO2 to HCO3− and H+ at the gill surface.

Branchial Ionic Uptake and Acid-Base Regulation in the Rainbow Trout, Salmo Gairdneri

1981 ◽  
Vol 92 (1) ◽  
pp. 289-303
Author(s):  
S. F. PERRY ◽  
M. S. HASWELL ◽  
D. J. RANDALL ◽  
A. P. FARRELL
Keyword(s):  
Rainbow Trout ◽  
Sodium Bicarbonate ◽  
Salmo Gairdneri ◽  
Hypercapnic Acidosis ◽  
Acid Base ◽  
Bathing Medium ◽  
Sodium Uptake ◽  
Chloride Uptake ◽  
Disulphonic Acid ◽  
Ionic Uptake

1. Amiloride (10−4 M) inhibited sodium uptake in rainbow trout by 78% and was associated with a pronounced acidosis and decreases in both plasma total CO2 (Tcoco2)* and [HCO3−]. 2. 4-acetamido-4′-iso-thiocyanatostilbene-2,2′ disulphonic acid (SITS) (10−4M) in the bathing medium inhibited chloride uptake by 66% and following 6 h a significant decrease in plasma [H+] and significant increases in TCOCO2 and [HCO3−] were observed. 3. Inhibition of chloride uptake (50%) with external sodium bicarbonate (12 mM) resulted in a more rapid and pronounced alkalosis than did SITS inhibition. 4. Hypercapnic acidosis had no significant effect on the rates of branchial sodium and chloride uptake. 5. Increasing the concentration of sodium in the bathing water resulted in a less pronounced acidosis and a more rapid pH recovery during hypercapnia. 6. These results are discussed with reference to the gill as an acid-base regulating structure. These findings are consistent with a gill model previously presented by Haswell, Randall & Perry (1980).

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