Bicarbonate Reabsorption in the Proximal Tubule during Carbonic Anhydrase Inhibition

1984 ◽  
Vol 429 (1 Biology and C) ◽  
pp. 538-540 ◽  
Author(s):  
MARTIN G. COGAN
Keyword(s):  
Carbonic Anhydrase ◽  
Proximal Tubule ◽  
Bicarbonate Reabsorption ◽  
Carbonic Anhydrase Inhibition

Effect of carbonic anhydrase inhibition on proximal tubular bicarbonate reabsorption

1963 ◽  
Vol 205 (4) ◽  
pp. 693-696 ◽  
Author(s):  
James R. Clapp ◽  
John F. Watson ◽  
Robert W. Berliner
Keyword(s):  
Carbonic Anhydrase ◽  
Proximal Tubule ◽  
Intravenous Administration ◽  
Distal Portion ◽  
Bicarbonate Concentration ◽  
Plasma Bicarbonate ◽  
Bicarbonate Reabsorption ◽  
Carbonic Anhydrase Inhibition ◽  
Before And After ◽  
Proximal Tubular

Samples of fluid from the proximal tubule were collected for the measurement of pH and bicarbonate concentration before and after the administration of acetazolamide (Diamox). Samples collected before acetazolamide were consistently more acid than plasma with the most acid samples coming from the more distal portion of the proximal tubule. After the intravenous administration of acetazolamide, the pH and bicarbonate concentration were consistently higher than in plasma. Bicarbonate concentrations as high as 2.8 times that in plasma were observed. The rise in proximal tubular fluid bicarbonate concentration after acetazolamide is presumably due to a reduction in the rate of bicarbonate reabsorption out of proportion to any impairment in proximal tubular fluid volume reduction.

Carbonic anhydrase-dependent bicarbonate reabsorption in the rat proximal tubule

1979 ◽  
Vol 236 (1) ◽  
pp. F58-F65 ◽  
Author(s):  
M. S. Lucci ◽  
D. G. Warnock ◽  
F. C. Rector
Keyword(s):  
Carbonic Anhydrase ◽  
Dose Response ◽  
Response Curve ◽  
Carbonic Acid ◽  
Co2 Concentration ◽  
Bicarbonate Reabsorption ◽  
Perfusion Solution ◽  
Carbonic Anhydrase Inhibition ◽  
Rat Proximal Tubule

The extent to which bicarbonate reabsorption in the rat proximal convoluted tubule depends on carbonic anhydrase has been examined by in vivo microperfusion and the measurement of total CO2 concentration by microcalorimetry. Tubules were perfused with an ultrafiltrate-like solution at 13 nl/min, and volume reabsorptive rate (JV) was measured using [14C]inulin. Addition of either 800 or 100 microM acetazolamide to the perfusion solution completely inhibited the reabsorption of total CO2. The control total CO2 reabsorptive rate (JtCO2) was 147 +/- 23 pmol/mm.min, and acetazolamide reduced JtCO2 to -3 +/- 5 pmol/mm.min. Acetazolamide reduced JV by 65% from a control of 2.3 +/- 0.4 to 0.8 +/- 0.1 nl/mm.min. The dose-response curve for acetazolamide showed that the I50 for inhibition of JtCO2 was 4 microM. The inactive congener of acetazolamide, t-butyl acetazolamide, did not reduce JV or inhibit bicarbonate reabsorption, indicating that the effect of acetazolamide on JtCO2 was specific for carbonic anhydrase inhibition. Since bicarbonate reabsorption was completely blocked by carbonic anhydrase inhibition, there is no need to postulate either carbonic acid recycling or carbonic anhydrase-independent bicarbonate reabsorption.

Effects of CO2 and acetazolamide on bicarbonate and fluid transport in rabbit proximal tubules

1981 ◽  
Vol 240 (1) ◽  
pp. F54-F62 ◽  
Author(s):  
H. R. Jacobson
Keyword(s):  
Carbonic Anhydrase ◽  
Fluid Transport ◽  
Proximal Tubules ◽  
Rabbit Kidney ◽  
Bicarbonate Reabsorption ◽  
Carbonic Anhydrase Inhibition ◽  
Acute Changes

Early superficial (SF) and juxtamedullary (JM) proximal convolutions of the rabbit kidney were perfused in vitro to determine the effects of carbonic anhydrase inhibition (10(-4) M acetazolamide) and acute changes in PCO2 (decreases to approximately equal to 15 and increases to approximately equal to 74 mmHg) on potential differences (PD in mV), volume reabsorption (Jv in nl x mm-1 x min-1), and bicarbonate reabsorption (JCO2 in pmol x mm-1 x min-1). At PCO2 37 mmHg early JM exhibited a more lumen-negative PD (-7.5 vs. -5.3), greater Jv (1.13 vs. 0.82), and greater JCO2 (86.7 vs. 44.4) than early Sf. Sf and JM had similar responses to acetazolamide: PD became more negative (-5.2 to -5.9 in SF; -8.8 to -10.1 in JM), Jv decreased (0.92 to 0.68 in SF; 1.11 to 0.76 in JM), and JCO2 decreased (35.7 to 7.7 in SF; 99.2 to 27.4 in JM). Increasing PCO2 to approximately equal to 74 mmHg decreased lumen-negative PD, increased Jv, and increased JCO2 in SF and JM (-5.5 to -4.8, 0.72 to 0.95, and 47.6 to 80.4 in SF; -6.6 to -5.7, 1.19 to 1.47, and 78.0 to 111.3 in JM). Decreasing PCO2 to approximately equal to 15 mmHg increased lumen-negative PD, decreased JCO2, but had no effect on Jv in both segments (-4.9 to -5.8, 51.3 to 6.3, and 0.80 to 0.79 in SF; -7.0 to -7.9, 75.3 to 19.6, and 1.34 to 1.41 in JM). It is concluded that 1) early SF and JM display quantitative heterogeneity, 2) PCO2 changes within the physiologic range produce large changes in HCO3 absorption in early proximal tubules and 3) large changes in HCO3- reabsorption are dissociated from changes in volume reabsorption during hypocapnia.

scholarly journals The mechanism of bicarbonate reabsorption in the proximal and distal tubules of the kidney. 1965.

1998 ◽  
Vol 9 (6) ◽  
pp. 1134-1145
Author(s):  
F C Rector ◽  
N W Carter ◽  
D W Seldin
Keyword(s):  
Steady State ◽  
Carbonic Anhydrase ◽  
Proximal Tubule ◽  
Intravenous Injection ◽  
Distal Tubule ◽  
Ph Sensitive ◽  
Tubular Cells ◽  
Bicarbonate Reabsorption ◽  
Luminal Membrane ◽  
Distal Tubules

The mechanism of HCO3- reabsorption in proximal and distal tubules was examined in rats undergoing NaHCO3 diuresis. The steady-state intratubular pH was measured with pH-sensitive glass microelectrodes and compared with the equilibrium pH calculated from the HCO3- concentration of the tubular fluid (measured with quinhydrone electrodes) and plasma Pco2. In the proximal tubule the intratubular pH and the equilibrium pH were identical, indicating no accumulation of excess H2CO3. After inhibition of carbonic anhydrase, however, intratubular pH was significantly lower (0.85 pH U) than the equilibrium pH. It was concluded that HCO3- reabsorption in the proximal tubule was mediated by H+ secretion, but that carbonic anhydrase located in the luminal membrane of the cell prevented H2CO3 from accumulating in the tubular fluid. In the distal tubule the intratubular pH was 0.85 U lower than the equilibrium pH. This difference could be obliterated by an intravenous injection of carbonic anhydrase. It was concluded that HCO3- reabsorption in this segment was also accomplished by H+ secretion. The accumulation of excess H2CO3 in the tubular fluid indicated that, in contrast to the proximal tubule, carbonic anhydrase was not located in the luminal membrane of distal tubular cells.

Function of proximal tubule carbonic anhydrase defined by selective inhibition

1983 ◽  
Vol 245 (4) ◽  
pp. F443-F449 ◽  
Author(s):  
M. S. Lucci ◽  
J. P. Tinker ◽  
I. M. Weiner ◽  
T. D. DuBose
Keyword(s):  
Carbonic Anhydrase ◽  
Proximal Tubule ◽  
Enzyme Inhibitor ◽  
Co2 Concentration ◽  
Selective Inhibition ◽  
Bicarbonate Reabsorption ◽  
Simultaneous Inhibition ◽  
Microelectrode Techniques

The specific role of luminal carbonic anhydrase in bicarbonate reabsorption by the proximal tubule has not been established because it has been difficult to inhibit selectively the luminal enzyme without simultaneous inhibition of the cytoplasmic enzyme. The present experiments employed in vivo microperfusion, microcalorimetry, and microelectrode techniques to determine the effects of luminal application of a dextran-bound carbonic anhydrase inhibitor (DBI) on bicarbonate reabsorptive rate (JtCO2) and intraluminal pH in the rat proximal convoluted tubule. Tubules were perfused at 20 nl/min with an artificial ultrafiltrate. Aminoethyl dextran (AED) with no enzyme-inhibitor activity was added to the control perfusate, and the effects of the parent inhibitor STZ not bound to dextran were also determined. Both DBI and STZ significantly reduced JtCO2 from 138 ⁺/⁻ 10 pmol X mm-1 X min-1 (control) to 30 ⁺/⁻ 4 and 30 ⁺/⁻ 9, respectively. In contrast to the indistinguishable effects on JtCO2, intraluminal pH measured close to the site of perfusion was 6.80 ⁺/ 0.02 during DBI perfusion, whereas with STZ perfusion the pH was 7.24 ⁺/⁻ 0.04 (P less than 0.001). Using the collected perfusate total CO2 concentration and a renal cortical PCO2 of 60 mmHg, the calculated equilibrium pH for this solution was 7.27. DBI inhibited only luminal carbonic anhydrase, therefore. We conclude that luminal carbonic anhydrase is in functional contact with proximal tubule fluid and is necessary for at least 80% of bicarbonate reabsorption by this segment.(ABSTRACT TRUNCATED AT 250 WORDS)

1123: Renal Oxalate Transport Depends on Local Carbonic Anhydrase Activity in the Proximal Tubule

2004 ◽  
Vol 171 (4S) ◽  
pp. 296-296
Author(s):  
Michael Straub ◽  
Joséphine Befolo-Elo ◽  
Richard E Hautmann ◽  
Edgar Braendle
Keyword(s):  
Carbonic Anhydrase ◽  
Proximal Tubule ◽  
Carbonic Anhydrase Activity ◽  
Oxalate Transport

Coumaronochromone as antibacterial and carbonic anhydrase inhibitors from Aerva persica (Burm.f.) Merr.: experimental and first-principles approaches

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Muhammad Imran ◽  
Ahmad Irfan ◽  
Mohammed A. Assiri ◽  
Sajjad H. Sumrra ◽  
Muhammad Saleem ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
First Principles ◽  
Molecular Electrostatic Potential ◽  
Chemical Constituents ◽  
Bacterial Strains ◽  
Hirshfeld Analysis ◽  
Carbonic Anhydrase Inhibition ◽  
Inhibition Studies ◽  
Lowest Unoccupied Molecular Orbitals

AbstractThe Aerva plants are exceptionally rich in phytochemicals and possess therapeutics potential. Phytochemical screening shows that Aerva persica (Burm.f.) Merr. contains highest contents i.e., total phenolics, flavonoids, flavonols, tannins, alkaloids, carbohydrates, anthraquinones and glycosides. In-vitro antibacterial and enzymatic (carbonic anhydrase) inhibition studies on methanol extracts of A. persica indicated the presence of biological active constituents within chloroform soluble portions. Investigation in the pure constituents on the chloroform portions of A. persica accomplished by column chromatography, NMR and MS analysis. The bioguided isolation yields four chemical constituents of coumaronochromone family, namely aervin (1-4). These pure chemical entities (1-4) showed significant antibacterial activity in the range of 60.05–79.21 µg/ml against various bacterial strains using ampicillin and ciprofloxacin as standard drugs. The compounds 1-4 showed promising carbonic anhydrase inhibition with IC50 values of 19.01, 18.24, 18.65 and 12.92 µM, respectively, using standard inhibitor acetazolamide. First-principles calculations revealed comprehensive intramolecular charge transfer in the studied compounds 1-4. The spatial distribution of highest occupied and lowest unoccupied molecular orbitals, ionization potential, molecular electrostatic potential and Hirshfeld analysis revealed that these coumaronochromone compounds would be proficient biological active compounds. These pure constituents may be used as a new pharmacophore to treat leaukomia, epilepsy, glaucoma and cystic fibrosis.

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