Pulmonary carbonic anhydrase in the human, monkey, and rat

The distribution of carbonic anhydrase in the human, monkey, and rat lung was studied by the histochemical method of Hansson. High activity of this enzyme was demonstrated in the endothelium of pulmonary capillaries. In the human and the monkey lung enzyme activity was exhibited in the whole circumference of the capillaries, but in the rat enzyme activity is confined to capillary segments having close contact with alveolar epithelium forming the blood-air barrier. Staining was inhibited by 10 microM acetazolamide, but was not affected by 10 microM Cl 13,850, an inactive acetazolamide analogue. The location of carbonic anhydrase in the lung supports the idea that pulmonary carbonic anhydrase promotes CO2 elimination from the blood into the alveolar space. Its possible functions may be to act upon plasma to accelerate the conversion of HCO-3 to CO2 and to facilitate CO2 transport through the lung tissue.

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Rat lung carbonic anhydrase: activity, localization, and isozymes

Journal of Applied Physiology ◽

10.1152/jappl.1986.60.2.638 ◽

1986 ◽

Vol 60 (2) ◽

pp. 638-645 ◽

Cited By ~ 28

Author(s):

R. P. Henry ◽

S. J. Dodgson ◽

R. E. Forster ◽

B. T. Storey

Keyword(s):

Enzyme Activity ◽

Carbonic Anhydrase ◽

Carbonic Anhydrase Activity ◽

Hydration Reaction ◽

Rat Lung ◽

Cell Debris ◽

Blood Contamination ◽

Total Enzyme Activity ◽

Erythrocyte Lysis ◽

A Cell

sCarbonic anhydrase activity in rat lungs perfused free of blood was localized by homogenization of the tissue followed by differential centrifugation. Four fractions were obtained from the homogenate, a cell debris pellet with a mitochondrial pellet and a microsomal pellet with a clear cytosol supernatant. The last named fraction contained 67% of the total enzyme activity; the cell debris contained 18%, and the mitochondrial and microsomal contained 8 and 7%, respectively. Of the 33% of enzyme activity associated with the pellet fraction, 25% could be experimentally defined as membrane associated by its solubilization with 0.3 M tris-(hydroxymethyl) aminoethane sulfate buffer. The remainder was defined as membrane bound. Purification of the soluble carbonic anhydrase from the lung yielded two isozymes with electrophoretic and inhibitor sensitivities apparently identical with the blood isozymes. Hemoglobin analysis showed that the lung isozymes could not have included more than 0.03% enzyme from blood contamination. The carbonic anhydrase activity present in the whole rat lung would give an average acceleration of the CO2 hydration reaction under physiological conditions over the uncatalyzed rate of 122, sufficient to maintain equilibration between CO2 and plasma HCO3- during blood transit of the lung. If the membrane-associated activity is mostly on the plasma membrane of the endothelial cells and available to the capillary blood, it would be sufficient to give this acceleration. We suggest that the possible source of this membrane-associated activity might be adsorption from the blood of carbonic anhydrase liberated by erythrocyte lysis.

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Evidence for active sodium transport across alveolar epithelium of isolated rat lung

Journal of Applied Physiology ◽

10.1152/jappl.1987.62.6.2460 ◽

1987 ◽

Vol 62 (6) ◽

pp. 2460-2466 ◽

Cited By ~ 81

Author(s):

B. E. Goodman ◽

K. J. Kim ◽

E. D. Crandall

Keyword(s):

Sodium Transport ◽

Alveolar Epithelial Cell ◽

Control Period ◽

Alveolar Epithelium ◽

Rat Lung ◽

Alveolar Space ◽

Active Sodium ◽

Apparent Permeability ◽

Lung Weight ◽

Active Sodium Transport

We have previously presented evidence that cultured alveolar epithelial cell monolayers actively transport sodium from medium to substratum, a process that can be inhibited by sodium transport blockers and stimulated by beta-agonists. In this study, the isolated perfused rat lung was utilized in order to investigate the presence of active sodium transport by intact adult mammalian alveolar epithelium. Radioactive tracers (22Na and [14C]sucrose) were instilled into the airways of isolated Ringer-perfused rat lungs whose weight was continuously monitored. The appearance of isotopes in the recirculated perfusate was measured, and fluxes and apparent permeability-surface area products were determined. A pharmacological agent (amiloride, ouabain, or terbutaline) was added to the perfusate during each experiment after a suitable control period. Amiloride and ouabain resulted in decreased 22Na fluxes and a faster rate of lung weight gain. Terbutaline resulted in increased 22Na flux and a more rapid rate of lung weight loss. [14C]sucrose fluxes were unchanged by the presence of these pharmacological agents. These data are most consistent with the presence of a regulable active component of sodium transport across intact mammalian alveolar epithelium that leads to removal of sodium from the alveolar space, with anions and water following passively. Regulation of the rate of sodium and fluid removal from the alveolar space may play an important role in the prevention and/or resolution of alveolar pulmonary edema.

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A micromethod for measuring carbonic anhydrase activity using 18O exchange between CO2 and H2O

Journal of Applied Physiology ◽

10.1152/jappl.1988.65.4.1902 ◽

1988 ◽

Vol 65 (4) ◽

pp. 1902-1906 ◽

Cited By ~ 3

Author(s):

N. Bitterman ◽

L. Lin ◽

R. E. Forster

Keyword(s):

Enzyme Activity ◽

Carbonic Anhydrase ◽

High Activity ◽

Intact Cell ◽

Porous Membrane ◽

Carbonic Anhydrase Activity ◽

Published Data ◽

Hydration Reaction ◽

Activity Type ◽

Reaction Velocity

We have developed a method of measuring the activity and characteristics of carbonic anhydrase (CA) using the disappearance of 18O from CO2 in 1 ml of gas contained in a glass chamber as it exchanges with H2O in 0.01 ml 0.25 M NaHCO3 solution in a thin (25 micron) porous membrane. Serial gas samples (approximately 0.02 ml) are analyzed in a mass spectrometer to obtain the rate of disappearance of the label. The enzyme activity can be measured inside intact cell or particle membranes. As little as 10(-15) mol of high-activity type CA can be detected at 25 degrees C, and the activity of 200 times this amount can be measured. The uncatalyzed hydration reaction velocity constant was 0.056 +/- 0.004 s-1, in agreement with published data.

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Ultrastructure of pulmonary microvasculature in acute endotoxemia

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100083217 ◽

1978 ◽

Vol 36 (2) ◽

pp. 470-471

Author(s):

R. G. Gerrity ◽

M. Richardson

Keyword(s):

Polymorphonuclear Leukocytes ◽

Alveolar Epithelium ◽

Endothelial Damage ◽

Capillary Endothelium ◽

Type Ii Cells ◽

Type Ii ◽

Interstitial Edema ◽

Pulmonary Capillaries ◽

Lung Ultrastructure ◽

Fibrin Thrombi

Dogs were injected intravenously with E_. coli endotoxin (2 mg/kg), and lung samples were taken at 15 min., 1 hr. and 24 hrs. At 15 min., occlusion of pulmonary capillaries by degranulating platelets and polymorphonuclear leukocytes (PML) was evident (Fig. 1). Capillary endothelium was intact but endothelial damage in small arteries and arterioles, accompanied by intraalveolar hemorrhage, was frequent (Fig. 2). Sloughing of the surfactant layer from alveolar epithelium was evident (Fig. 1). At 1 hr., platelet-PML plugs were no longer seen in capillaries, the endothelium of which was often vacuolated (Fig. 3). Interstitial edema and destruction of alveolar epithelium were seen, and type II cells had discharged their granules into the alveoli (Fig. 4). At 24 hr. phagocytic PML's were frequent in peripheral alveoli, while centrally, alveoli and vessels were packed with fibrin thrombi and PML's (Fig. 5). In similar dogs rendered thrombocytopenic with anti-platelet serum, lung ultrastructure was similar to that of controls, although PML's were more frequently seen in capillaries in the former (Fig. 6).

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Entrapment of the Fastest Known Carbonic Anhydrase with Biomimetic Silica and Its Application for CO2 Sequestration

Polymers ◽

10.3390/polym13152452 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2452

Author(s):

Chia-Jung Hsieh ◽

Ju-Chuan Cheng ◽

Chia-Jung Hu ◽

Chi-Yang Yu

Keyword(s):

Carbonic Anhydrase ◽

High Activity ◽

Co2 Sequestration ◽

Residual Activity ◽

Entrapment Efficiency ◽

Free Form ◽

Uncatalyzed Reaction ◽

The Stability ◽

Time Required

Capturing and storing CO2 is of prime importance. The rate of CO2 sequestration is often limited by the hydration of CO2, which can be greatly accelerated by using carbonic anhydrase (CA, EC 4.2.1.1) as a catalyst. In order to improve the stability and reusability of CA, a silica-condensing peptide (R5) was fused with the fastest known CA from Sulfurihydrogenibium azorense (SazCA) to form R5-SazCA; the fusion protein successfully performed in vitro silicification. The entrapment efficiency reached 100% and the silicified form (R5-SazCA-SP) showed a high activity recovery of 91%. The residual activity of R5-SazCA-SP was two-fold higher than that of the free form when stored at 25 °C for 35 days; R5-SazCA-SP still retained 86% of its activity after 10 cycles of reuse. Comparing with an uncatalyzed reaction, the time required for the onset of CaCO3 formation was shortened by 43% and 33% with the addition of R5-SazCA and R5-SazCA-SP, respectively. R5-SazCA-SP shows great potential as a robust and efficient biocatalyst for CO2 sequestration because of its high activity, high stability, and reusability.

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