Bicarbonate transport by isolated perfused rabbit proximal convoluted tubules

1977 ◽  
Vol 233 (4) ◽  
pp. F307-F314 ◽  
Author(s):  
M. Burg ◽  
N. Green
Keyword(s):  
Hydrogen Ion ◽  
Bicarbonate Transport ◽  
Fluid Absorption ◽  
The Mean ◽  
Tubule Cells ◽  
The Relationship ◽  
Convoluted Tubules ◽  
Mean Concentration ◽  
Proximal Convoluted Tubules

Proximal convoluted tubules were dissected from rabbit kidneys and perfused in vitro in order to investigate the relationship between the reabsorption of fluid and of bicarbonate. Bicarbonate was absorbed when it was initially present in the perfusate. At slow rates of perfusion the mean concentration of total CO2 was 9 mM in collected fluid with 25 mM bicarbonate in the bath. At faster rates of perfusion the mean rate of reabsorption was 13.6 pmol cm-1 tubule length s-1. Absorption of bicarbonate was inhibited to a large but not complete extent by elimination of sodium from the perfusate and bath or potassium from the bath, and by addition of ouabain. It was not inhibited by elimination of the organic solutes from the perfusate nor by elimination of chloride from the perfusate and bath. Considered with previous measurements of fluid absorption these results are consistent with the existence of a linked sodium-for-hydrogen ion exchange mechanism at the luminal border of the tubule cells, but there are other possibilities which are discussed. Additionally, the effect of acetazolamide was investigated. The drug virtually completely inhibited bicarbonate absorption and inhibited fluid absorption by 30-40%.

PTH inhibition of bicarbonate transport by proximal convoluted tubules

1980 ◽  
Vol 239 (2) ◽  
pp. F127-F134 ◽  
Author(s):  
T. D. McKinney ◽  
P. Myers
Keyword(s):  
Parathyroid Hormone ◽  
Cyclic Amp ◽  
Co2 Concentration ◽  
Bicarbonate Transport ◽  
Co2 Absorption ◽  
Fluid Absorption ◽  
Dibutyryl Cyclic Amp ◽  
Convoluted Tubules ◽  
Proximal Convoluted Tubules

These studies examined the effect of parathyroid hormone (PTH), dibutyryl cyclic AMP DBcAMP, and 8-bromo-cyclic AMP BrcAMP on HCO3- transport by rabbit superficial proximal convoluted tubules perfused in vitro. Bicarbonate was estimated as total CO2 measured microcalorimetrically. At slow perfusion rates with 25 mM HCO3- in the perfusate and bath, PTH (0.1 U/ml in the bath) caused the total CO2 in tubular fluid to rise from 10.2 to 19.9 mM. The hormone had no effect on the total CO2 concentration in tubules perfused with HCO3(-)-free perfusates. With HCO3(-) in the perfusate and bath, PTH reduced the rates of fluid and total CO2 absorption to 57 and 48% of control values, respectively. PTH had no effect on the rates of fluid absorption and total CO2 secretion when HCO3(-)-free perfusates were used. The effects of DBcAMP and BrcAMP (10(-7) M in the bath) were similar to those of PTH. 5'-AMP (10(-6) M in the bath) did not alter the total CO2 concentration of tubular fluid when the tubules were perfused at slow rates with HCO3- in the perfusate and bath. Ouabain (10(-5) M in the bath) caused the total CO2 concentration in tubules perfused at slow rates with HCO3--free perfusates to rise from 8.9 to 12.7 mM. PTH caused no further change in the total CO2 concentration in the presence of ouabain.

Organic solutes in fluid absorption by renal proximal convoluted tubules

1976 ◽  
Vol 231 (2) ◽  
pp. 627-637 ◽  
Author(s):  
M Burg ◽  
C Patlak ◽  
N Green ◽  
D Villey
Keyword(s):  
Epithelial Cell ◽  
Organic Solutes ◽  
Fluid Absorption ◽  
Transepithelial Voltage ◽  
Convoluted Tubules ◽  
Proximal Convoluted Tubules

Proximal convoluted tubules were dissected from rabbit kidneys and perfused with artificial solutions in vitro. The effect of various organic solutes on rate of fluid absorption and transepithelial voltage was tested by removing solutes from or adding them to perfusate and/or bath. Omission of albumin from the bath caused rate of fluid absorption to descrease 33% without any change in voltage. Omission of glucose, lactate, alanine, and citrate from the bath had no effect. In contrast, when they were removed from perfusate, rate of fluid absorption fell by 45-75% (depending on whether they were replaced by NaCl or mannitol and NaCl), and voltage (normally negative in lymen) decreased to near zero. Adding glucose or alanine individually to perfusate caused a small increase in rate of fluid absorption and a relatively large increase in voltage. alpha-Methyl-D-glucoside and cycloleucine (which are transported but not metabolized) had effects similar to glucose and alanine, except that voltage changes were not as great. Phlorizin (10(-5) M in perfusate) had the same effect as removing glucose from perfusate. When glucose and alanine were added to perfusate, epithelial cell swelled significantly. Lactate and citrate also caused rate of fluid absorption to increase when they were added to perfusate, but they did not affect transepithelial voltage nor did they cause cells to swell significantly. Possible mechanisms of these effects and the role of organic solutes in fluid absorption by proximal convoluted tubules are discussed.

scholarly journals Sensitivity of Rhizoctonia solani AG-2-2 from Sugar Beet to Fungicides

Plant Disease ◽  
2016 ◽  
Vol 100 (12) ◽  
pp. 2427-2433 ◽  
Author(s):  
Sahar Arabiat ◽  
Mohamed F. R. Khan
Keyword(s):  
Sugar Beet ◽  
Rhizoctonia Solani ◽  
Root Rot ◽  
The United States ◽  
Damping Off ◽  
Growth Assay ◽  
The Mean ◽  
Crown And Root Rot ◽  
Mean Concentration

Rhizoctonia damping-off and crown and root rot caused by Rhizoctonia solani are major diseases of sugar beet (Beta vulgaris L.) worldwide, and growers in the United States rely on fungicides for disease management. Sensitivity of R. solani to fungicides was evaluated in vitro using a mycelial radial growth assay and by evaluating disease severity on R. solani AG 2-2 inoculated plants treated with fungicides in the greenhouse. The mean concentration that caused 50% mycelial growth inhibition (EC50) values for baseline isolates (collected before the fungicides were registered for sugar beet) were 49.7, 97.1, 0.3, 0.2, and 0.9 μg ml−1 and for nonbaseline isolates (collected after registration and use of fungicides) were 296.1, 341.7, 0.9, 0.2, and 0.6 μg ml−1 for azoxystrobin, trifloxystrobin, pyraclostrobin, penthiopyrad, and prothioconazole, respectively. The mean EC50 values of azoxystrobin, trifloxystrobin, and pyraclostrobin significantly increased in the nonbaseline isolates compared with baseline isolates, with a resistant factor of 6.0, 3.5, and 3.0, respectively. Frequency of isolates with EC50 values >10 μg ml−1 for azoxystrobin and trifloxystrobin increased from 25% in baseline isolates to 80% in nonbaseline isolates. Although sensitivity of nonbaseline isolates of R. solani to quinone outside inhibitors decreased, these fungicides at labeled rates were still effective at controlling the pathogen under greenhouse conditions.

Binding of 63Ni(II) to Ultrafiltrable Constituents of Rabbit Serum In Vivo and In Vitro

1975 ◽  
Vol 21 (4) ◽  
pp. 521-527 ◽  
Author(s):  
Noritake Asato ◽  
Maria van Soestbergen ◽  
F William Sunderman
Keyword(s):  
Rabbit Serum ◽  
Total Serum ◽  
In Vivo Experiments ◽  
The Mean ◽  
Layer Chromatography ◽  
In Vivo Administration ◽  
Mean Concentration

Abstract Binding of 63Ni(Il) to ultrafiltrable constituents of rabbit serum was studied (a) after in vitro incubation (2 h, 37 °C) of rabbit serum with 63NiCl2 (10-100 µmol/liter), and (b) at intervals (0.25-2 h) after in vivo administration of 63NiCl2 (40-160 µmol/kg body wt, i.v.). Serum ultrafiltrates were fractionated by thin-layer chromatography, and the separated compounds made visible by autoradiography and by ninhydrin staining. Several (≃5) ultrafiltrable 63Ni-complexes were demonstrable as distinct radiodense 63Ni-bands with chromatographic mobilities corresponding to those of ninhydrin-positive bands. Unbound 63Ni(II) was not detected in serum ultrafiltrates in either the in vitro or in vivo experiments. In sera (n = 10) incubated in vitro with 63Ni(II) (10 µmol/ liter), the mean percentage of ultrafiltrable 63Ni was 36% (range = 33-38) of total serum 63Ni. In contrast, in sera (n = 10) obtained 2 h after i.v. injection of 63Ni(II) (40 µmol/kg), the mean concentration of total serum 63Ni was 10.8 µmol/liter (range = 6-14), and the mean percentage of ultrafiltrable 63Ni was 15% (range = 9-21) of total serum 63Ni. The disparity between the percentages of ultrafiltrable 63Ni obtained in vitro and in vivo was obviated when the in vivo experiments were performed in rabbits bilaterally nephrectomized, with ligated common bile ducts. This investigation confirms the existence of several nickel receptors in serum ultrafiltrates and substantiates the role of ultrafiltrable complexes in the excretion of nickel.

Contribution of leaked load to solute transport by renal tubules

1978 ◽  
Vol 234 (6) ◽  
pp. F480-F484 ◽  
Author(s):  
D. G. Warnock ◽  
C. S. Patlak ◽  
M. B. Burg
Keyword(s):  
Substantial Part ◽  
Renal Tubules ◽  
In Vitro Perfusion ◽  
Tubule Lumen ◽  
Tubular Transport ◽  
Glomerular Filtrate ◽  
The Relationship ◽  
Convoluted Tubules ◽  
Filtered Load

Renal tubules reabsorb solutes from the glomerular filtrate. The relationship between "filtered load" and reabsorption has been previously discussed and analyzed in detail. One aspect which has not been emphasized, however, is that, when reabsorption of a solute causes its concentration (or activity) in the tubule lumen to decrease below the level in the blood, solute may enter the tubule down this concentration gradient adding a "leaked load" to the filtered load. The leaked load should be taken into account when quantifying tubular transport. In the present study we derived equations for estimating the leaked load and its contribution to transport. The importance of the leaked load of glucose in the rabbit proximal convoluted tubules is evaluated with parameters derived from in vitro perfusion and by solving the equations numerically. It is shown that, depending on the conditions, the leaked load of glucose may account for a substantial part of the glucose present in the tubule lumen and reabsorbed from the tubule. Also, the leaked load could conceivably be an important factor in the transport of other solutes such as lactase and bicarbonate in proximal tubules.

The relationship in ewes between voluntary food intake during pregnancy and forage intake during lactation and after weaning

1979 ◽  
Vol 28 (1) ◽  
pp. 25-39 ◽  
Author(s):  
Janet Z. Foot ◽  
A. J. F. Russel
Keyword(s):  
Dry Matter ◽  
Maternal Nutrition ◽  
Tritiated Water ◽  
Weight Changes ◽  
Forage Intake ◽  
The Mean ◽  
Daily Intakes ◽  
The Relationship ◽  
Lamb Growth

ABSTRACT(1) Voluntary intake of forage was measured in 31 Scottish Blackface ewes for the last 14 weeks of pregnancy, throughout lactation, and 15 weeks subsequently. During pregnancy 15 ewes were given hay and 16 dried grass (apparent dry-matter digestibilities in vitro were 51 and 69·6% respectively). All ewes were given the same dried grass during lactation and after weaning (digestibilities 75 and 73% respectively). Body fat was estimated from tritiated water space.(2) Pregnant ewes consumed twice as much digestible dry matter from dried grass (1028 g) as from hay (502 g). Intakes of ewes with twin and single foetuses were similar.(3) During lactation the mean daily intakes of dried grass were 2278, 2610,2612 and 2722 g dry matter respectively, for ewes that had been given dried grass in pregnancy and had single and twin lambs, and for those that had been given hay and had singles and twins. Differences between dried grass and hay were consistently significant (P < 0·01).(4) After weaning the intakes declined rapidly but their ranking remained similar.(5) Lamb birth weights were affected by nutrition during pregnancy, lamb growth rates within twins or singles were not influenced by maternal nutrition during pregnancy or lactation. Differences in ewe intakes during lactation were reflected in ewe body-weight changes.(6) For all ewes, up to 64% of the variation in intake during lactation could be related to factors prevailing before and at lambing (pregnancy diet, ewe weight and fat content) and during lactation (lamb gain and ewe weight change).

Effect of potassium on proximal tubular function

1978 ◽  
Vol 234 (5) ◽  
pp. F381-F385 ◽  
Author(s):  
J. Cardinal ◽  
D. Duchesneau
Keyword(s):  
Renal Tubule ◽  
Potential Difference ◽  
Tubular Function ◽  
Fluid Absorption ◽  
Bathing Medium ◽  
Sodium Potassium ◽  
Proximal Tubular ◽  
Proximal Tubular Function ◽  
Convoluted Tubules

In order to study the effect of potassium on the renal tubule, proximal convoluted tubules were dissected from rabbit kidneys and perfused in vitro. Omitting potassium from both the perfusate and bath caused the rate of fluid absorption and the transtubular potential difference to fall to zero. This effect was due to the absence of potassium in the bathing medium since no change was observed when potassium was omitted from the perfusate only. With 0.5 and 1.0 meq/liter of potassium in the bath, there was still a significant decrease from control in both the potential difference and the rate of fluid absorption. With 2.5 meq/liter of potassium in the bath, the results did not differ from control. In further studies, tubules were perfused with 10 meq/liter of potassium in both perfusate and bath. There was no change in the potential difference of fluid absorption. These results are consistent with the view that active transtubular transport of sodium is linked to the influx of potassium into the cell at the peritubular membrane and that this is probably mediated by sodium-potassium-ATPase. Our results also suggest that the variations of potassium concentration in the physiological range do not affect proximal tubular function.

Potassium conductance regulation by pH during volume regulation in rabbit proximal convoluted tubules

1992 ◽  
Vol 263 (3) ◽  
pp. F453-F458 ◽  
Author(s):  
J. S. Beck ◽  
S. Breton ◽  
G. Giebisch ◽  
R. Laprade
Keyword(s):  
Intracellular Ph ◽  
Basolateral Membrane ◽  
Potassium Conductance ◽  
Membrane Resistance ◽  
Disulfonic Acid ◽  
Bicarbonate Transport ◽  
Hypotonic Shock ◽  
Reduction Of Co2 ◽  
Convoluted Tubules ◽  
Proximal Convoluted Tubules

When rabbit proximal convoluted tubules were microperfused in the presence of bicarbonate, a 90 mosmol hypotonic shock hyperpolarized the basolateral membrane by 5.5 +/- 1.4 mV, increased basolateral potassium selectivity (tK) from 0.30 +/- 0.02 to 0.45 +/- 0.02, and reduced the basolateral membrane resistance from 4,887 +/- 821 to 2,836 +/- 602 omega.cm. These data show that the hypotonic shock increased absolute basolateral potassium conductance. The same hypotonic shock elevated intracellular pH from 7.18 +/- 0.04 to 7.31 +/- 0.04. When bath pH was increased by 0.2 pH units (by reduction of CO2), intracellular pH rose by 0.13 +/- 0.01. In separate experiments this maneuver hyperpolarized the basolateral membrane by 5.0 +/- 0.8 mV and augmented basolateral tK from 0.58 +/- 0.06 to 0.68 +/- 0.04, suggesting that the basolateral potassium conductance is sensitive to pH changes of a magnitude similar to that evoked by a hypotonic shock. In the nominal absence of bicarbonate or presence of 0.5 mM 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) in the bath, the hypotonic shock caused a transient intracellular acidification, suggesting involvement of basolateral bicarbonate transport in the hypotonic shock-induced alkalinization. In the absence of bicarbonate, the hypotonic shock did not increase basolateral tK or induce hyperpolarization of the basolateral membrane. We conclude that the increase in potassium conductance observed during hypotonic shock is at least partly mediated by a bicarbonate-dependent, SITS-sensitive intracellular alkalinization.

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