Renal proximal tubule of flounder. I. Physiological properties

1986 ◽  
Vol 250 (4) ◽  
pp. R608-R615 ◽  
Author(s):  
K. W. Beyenbach ◽  
D. H. Petzel ◽  
W. H. Cliff
Keyword(s):  
Epithelial Transport ◽  
Winter Flounder ◽  
Transport Systems ◽  
Pseudopleuronectes Americanus ◽  
Physiological Properties ◽  
Secretory Transport ◽  
Transepithelial Voltage ◽  
Electrochemical Potentials ◽  
Leaky Epithelium

The proximal segment of the winter flounder, Pseudopleuronectes americanus, was investigated. Isolated tubules net secrete fluid, although at low rates, 37 pl X min-1 X mm-1. The dominant ions in secreted fluid are Na and Cl, with [Cl] significantly higher than in the bath. Mg and SO4 concentrations in secreted fluid are more than 10-fold greater than in the bath. The transepithelial voltage (-1.9 mV) and resistance (26 omega X cm2) indicate an electrically leaky epithelium, and transepithelial diffusion potentials suggest the Na selectivity of the paracellular pathway. Transepithelial electrochemical potentials point to active transport of Mg, SO4, and probably also Cl and to transepithelial equilibrium of Na. Failure to observe any secretory transport in tubules perfused in vitro at the commonly used perfusion rates illustrates the necessity of low, preferably subnanoliter, perfusion rates in detecting and studying low-capacity epithelial transport systems by the method of Burg.

‘Facilitation’ of Melanophore Responses in Winter Flounder Pseudopleuronectes Americanus

1992 ◽  
Vol 168 (1) ◽  
pp. 289-299
Author(s):  
D. BURTON ◽  
M. P. O'DRISCOLL
Keyword(s):  
Response Rates ◽  
Winter Flounder ◽  
Repeated Injection ◽  
Pseudopleuronectes Americanus ◽  
Black And White ◽  
Skin Samples

Melanophores of winter flounder (Pseudopleuronectes americanus) subjected to repeated transfers between black and white backgrounds display pronounced enhancement of the rates of melanosome aggregation and dispersion. Melanosome aggregation in response to repeated injection of noradrenaline displays a similar enhancement. In vitro preparations of microscopic skin samples on scales removed during successive cycles of background changes also display increasing melanophore response rates to K+ stimulation. It is concluded that a physiological ‘priming’ mechanism is involved peripherally at the melanophore level and it is proposed that this represents a form of facilitation. Also, it is deduced from these experiments that a modulation of the microtubular channels associated with melanosome translocation is probably the basis of the facilitation process.

Renal sugar transport in the winter flounder: V. secretion of 2-deoxy-D-galactose

1978 ◽  
Vol 234 (5) ◽  
pp. F424-F431
Author(s):  
J. B. Pritchard ◽  
G. Booz ◽  
A. Kleinzeller
Keyword(s):  
Sugar Transport ◽  
Winter Flounder ◽  
Free Sugar ◽  
Renal Tubules ◽  
Pseudopleuronectes Americanus ◽  
Clearance Ratio ◽  
Renal Handling ◽  
Cell Clearance

Isolated renal tubules and renal clearance techniques were used to characterize the renal handling of 2-deoxy-D-galactose (2-d-Gal) by the winter flounder (Pseudopleuronectes americanus). In vitro, energy-dependent, pH-sensitive uptake of 2-d-Gal (2–100 micron) was seen at the antiluminal face of the cell. Clearance measurements showed net secretion of 2-d-Gal in vivo. The mean clearance of 2-d-Gal in 18 fish was 0.98 +/- 0.16 ml/h while the glomerular filtration rate (GFR) was only 0.37 +/- 0.10 ml/h. Secretion was associated with marked renal accumulation of both 2-d-Gal and phosphorylated derivatives (2-d-Gal-1-phosphate). Tissue-to-plasma ratios (T/P) averaged 19 for free sugar and 59 for total sugar. Both clearance ratio and T/P were reduced to approximately 1 by injection of galactose (2.5 mmol/kg) simultaneously with 2-d-Gal (25 mumol/kg). Phlorizin (2.5 mumol/kg) increased net 2-d-Gal secretion, whereas glucose (2.5 mmol/kg) produced no change in secretion. Both compounds depressed 2-d-Gal T/P. This result suggests the presence of readsorptive transport at the brush border, sensitive to glucose and phlorizin.

Melanophore β-adrenoceptors in patterning in a flatfish, Pseudopleuronectes americanus

2007 ◽  
Vol 85 (6) ◽  
pp. 695-702 ◽  
Author(s):  
D. Burton
Keyword(s):  
Salt Solution ◽  
Winter Flounder ◽  
Dark Band ◽  
Pigment Dispersion ◽  
In Vitro Experiments ◽  
Pseudopleuronectes Americanus ◽  
Adrenoceptor Agonists

In vitro experiments were performed on melanophores bourne on scale slips sampled from three major areas (general background, dark band, and white spot) of the integumentary pattern of winter flounder, Pseudopleuronectes americanus (Walbaum, 1792). The effects of the respective β1- and β2-adrenoceptor agonists dobutamine and terbutaline and antagonists atenolol and ICI 118551 on pattern-related melanosome aggregation in response to exogenously applied L-noradrenaline were determined, as well as their effects on melanosome dispersion in balanced salt solution. The results demonstrate β1-adrenoceptor mediation in flatfish melanosome dispersion, with pattern-related variation, and also provide further evidence for β2-subtype involvement. Based on mammalian physiology, two β-subtypes will facilitate melanophore responsiveness to both neural and circulatory catecholamines. The in vivo role of these β-subtypes is discussed in relation to previously described attributes of the patterning behaviour of this species, which incorporates balances between α- and β-adrenoceptors. Dark band melanophores display a β-adrenoceptor bias, in contrast with other areas of the pattern, which would be consistent with their capacity for pigment dispersion in stressed flounders and with the slow paling of these bands during background-related responses.

Sugar absorption and secretion by winter flounder intestine

1981 ◽  
Vol 240 (5) ◽  
pp. G392-G400
Author(s):  
R. J. Naftalin ◽  
A. Kleinzeller
Keyword(s):  
Sugar Transport ◽  
Winter Flounder ◽  
Transport Systems ◽  
Secretory Process ◽  
Free Sugar ◽  
Pseudopleuronectes Americanus ◽  
Experimental Conditions ◽  
Sugar Absorption ◽  
Net Flux ◽  
Secretory System

Transport of sugars by winter flounder (Pseudopleuronectes americanus) intestine has been examined, and the following observations have been made. 1) No net absorption of D-galactose was found in controls; however, mucosally applied 0.1 mM phlorizin stimulated the mucosal-serosal flux with net sugar secretion. 2) Net absorption of methyl glycosides was inhibited by D-galactose, 0.1 mM ouabain, and phlorizin (without induction of secretion). 3) Net secretion of 2-deoxy-D-galactose was found without cellular accumulation of free sugar. The secretory process had a Km of 10 mM and was inhibited by serosally applied 0.1 mM phloretin, bilateral replacement of Ringer Na+ by choline, serosal ouabain, and D-galactose. 4) No net absorption or secretion of 2-deoxy-D-glucose was found with a variety of experimental conditions. 5) At least two active transport systems for sugars appear to be operative in the flounder intestine: a conventional Na+-dependent sugar transport system across the brush border that allows net absorption and a Na+-dependent secretory system that apparently also operates across the mucosal border. Because D-galactose is transported by both systems, there is no net flux of this sugar. Several possible models for the net secretory system are discussed.

scholarly journals Mechanisms responsible for the enhanced pumping capacity of the in situ winter flounder heart (Pseudopleuronectes americanus)

2007 ◽  
Vol 293 (5) ◽  
pp. R2112-R2119 ◽  
Author(s):  
Paula C. Mendonça ◽  
A. Gaylene Genge ◽  
Eric J. Deitch ◽  
A. Kurt Gamperl
Keyword(s):  
Cardiac Output ◽  
Power Output ◽  
High Volume ◽  
Filling Pressure ◽  
Winter Flounder ◽  
Mass Ratio ◽  
Pseudopleuronectes Americanus ◽  
Output Pressure

In situ Starling and power output curves and in vitro pressure-volume curves were determined for winter flounder hearts, as well as the hearts of two other teleosts (Atlantic salmon and cod). In situ maximum cardiac output was not different between the three species (∼62 ml·min−1·kg−1). However, because of the small size of the flounder heart, maximum stroke volume per milliliter per gram ventricle was significantly greater (2.3) compared with cod (1.7) and salmon (1.4) and is the highest reported for teleosts. The maximum power output of the flounder heart (7.6 mW/g) was significantly lower than that measured in the salmon (9.7) and similar to the cod (7.8) but was achieved at a much lower output pressure (4.9 vs. 8.0 and 6.2 kPa, respectively). Although the flounder heart could not perform resting levels of cardiac function at subambient pressures, it was much more sensitive to filling pressure, a finding supported by pressure-volume curves, which showed that the flounder's heart chambers were more compliant. Finally, we report that the flounder's bulbus:ventricle mass ratio (0.59) was significantly higher than in the cod (0.37) and salmon (0.22). These data, which support previous studies suggesting that the flatfish cardiovascular system is a high-volume, low-pressure design, show that vis-à-fronte filling is not important in flatfish, and that some fish can achieve high levels of cardiac output by vis-à-tergo filling alone; and suggest that a large compliant bulbus assists the flounder heart in delivering extremely large stroke volumes at pressures that do not become limiting.

Renal sugar transport in the winter flounder. VI. Reabsorption of D-mannose

1982 ◽  
Vol 242 (4) ◽  
pp. F415-F422 ◽  
Author(s):  
J. B. Pritchard ◽  
G. W. Booz ◽  
A. Kleinzeller
Keyword(s):  
Plasma Concentrations ◽  
Sugar Transport ◽  
Winter Flounder ◽  
Pseudopleuronectes Americanus ◽  
Paralichthys Lethostigma ◽  
Southern Flounder ◽  
Cotransport System ◽  
Stimulation Experiments

The transport of D-mannose (Man) in flounder kidney was studied using renal clearance techniques in vivo and brush border membrane (BBM) vesicles in vitro. At plasma concentrations of 50-100 microM Man, the winter flounder (Pseudopleuronectes americanus) reabsorbed up to 70% of the filtered sugar. Man phosphates, but not free Man, accumulated in renal cells. Reabsorption of Man was reduced by phlorizin, D-glucose, methyl-alpha-D-glucoside, methyl-alpha-D-mannoside, and 2-deoxy-D-glucose. In BBM vesicles a Na+-dependent, phlorizin-sensitive overshoot in Man uptake (10 microM) was seen. Na+-dependent Man uptake was saturable, with an apparent Km of 127 microM. The transport properties for Man were identical in BBM vesicles from the winter flounder and southern flounder (Paralichthys lethostigma). The transport specificity was determined by cis-inhibition and trans-stimulation experiments with BBM. Glucose, galactose, 1,5-anhydro-D-mannitol (i.e., 1-deoxymannose), 2-deoxy-2-fluoro-D-glucose, and methyl-alpha-mannoside were shown to share the carrier-mediating mannose transport. 2-Deoxyglucose, methyl-alpha-2-deoxy-D-glucoside, and both the isomers (alpha and beta) of methyl-D-glucoside did not. In contrast, alpha-methyl-D-glucoside inhibited D-glucose transport both in vivo and in BBM vesicles. It is concluded that Man reabsorption in the flounder occurs via a Na+-cotransport system that also handles glucose but that differs from the glucose/methyl-alpha-D-glucoside reabsorptive pathway in that 1) an oxygen on C-1 is not required, and 2) an axial configuration for -OH on C-2 (C1 conformation) is readily accommodated.

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