Inhibitor sensitivity of pulmonary vascular carbonic anhydrase

1993 ◽  
Vol 75 (4) ◽  
pp. 1642-1649 ◽  
Author(s):  
T. A. Heming ◽  
C. G. Vanoye ◽  
E. K. Stabenau ◽  
E. D. Roush ◽  
C. A. Fierke ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Carbonic Anhydrase ◽  
Luminal Surface ◽  
Membrane Permeation ◽  
Vascular Activity ◽  
Capillary Endothelial Cells ◽  
Membrane Bound ◽  
Co2 Excretion ◽  
Isolated Rat

The inhibitor sensitivity of pulmonary vascular carbonic anhydrase (CA) was examined in situ to identify the specific isozyme responsible for vascular activity and to study its distribution in the lung. Vascular CA activity was monitored in isolated rat lungs by measuring the rate of CO2 excretion and the magnitude of postcapillary CO2-HCO(3-)-H+ disequilibria. Lungs were perfused with isotonic salines containing gluconate, sulfate, Cl-, or I-, with or without sulfonamide derivatives. Effects of a CA inhibitor purified from porcine blood plasma were also determined. Vascular CA activity was unaffected by gluconate, sulfate, Cl-, and I- (< or = 100 mM). Sulfonamides with vastly different rates of membrane permeation (i.e., readily permeating ethoxzolamide, slowly permeating acetazolamide, and membrane-impermeant quaternary ammonium sulfanilamide) were capable of accessing all vascular CA with similar rates of access. The porcine inhibitor of CA (340 nM) produced a significant, but submaximal, inhibition of vascular CA activity. The data suggest that pulmonary vascular activity reflects a high-activity membrane-bound isozyme, CA IV, which is located on the extracellular luminal surface of capillary endothelial cells.

Endothelial and epithelial permeabilities to antipyrine in rat and dog lungs

1990 ◽  
Vol 258 (5) ◽  
pp. H1321-H1333
Author(s):  
W. O. Cua ◽  
G. Basset ◽  
F. Bouchonnet ◽  
R. A. Garrick ◽  
G. Saumon ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Temperature Effects ◽  
Permeability Coefficient ◽  
Physical State ◽  
Indicator Dilution ◽  
Dilution Technique ◽  
Isolated Cells ◽  
Physical And Mathematical Models ◽  
Isolated Rat

Temperature effects on the permeabilities of the structured endothelium and epithelium to antipyrine (AP) have been determined with the indicator dilution technique in isolated rat and dog lungs perfused between 38 and 8 degrees C. Permeability coefficients of the endothelium to AP [Pendo(AP)] from the Crone equation are smaller than values for isolated endothelial cells but close to the permeability coefficient of the interstitial epithelial plasmalemma [Pepi(AP)] obtained from physical and mathematical models. In these, tracer water is flow limited at the endothelium and the epithelium at all temperatures; AP is flow limited at the endothelium at T greater than 20 degrees C but barrier limited at the endothelium for T less than 20 degrees C and at the epithelium at all temperatures. At T less than 20 degrees C, log Pendo(AP) decreases regularly with 1/T, with a slope close to that found in cultured bovine pulmonary artery endothelial cells. At 15 degrees C, Pendo(AP) for the endothelial plasmalemma in situ is 30 X 10(-5) cm/s and is 56 X 10(-5) cm/s for the isolated cells in support of transcellular rather than paracellular passage. At T greater than 20 degrees C, log Pepi(AP) in situ decreases slightly with 1/T, with a discontinuity at T = 20 degrees C, and for T less than 20 degrees C, decreases with 1/T with a slope close to that of Pendo(AP). At 15 degrees C, Pepi(AP) is 2.8 X 10(-5) cm/s. The discontinuity may represent a change in the physical state of lipids in the interstitial plasmalemma of the epithelial cells.

CO2 excretion and postcapillary pH equilibration in blood-perfused turtle lungs

1999 ◽  
Vol 202 (8) ◽  
pp. 965-975
Author(s):  
E.K. Stabenau ◽  
T.A. Heming
Keyword(s):  
Carbonic Anhydrase ◽  
Anion Exchange ◽  
Cell Suspensions ◽  
Red Cell ◽  
Co2 Partial Pressure ◽  
Arterial Blood ◽  
Pass Perfusion ◽  
Erythrocyte Carbonic Anhydrase ◽  
Co2 Excretion

Turtles possess a significant postcapillary CO2 partial pressure (PCO2) disequilibrium between arterial blood and alveolar gas. There are several possible explanations for this blood disequilibrium including a slow rate of erythrocyte physiological anion shift (Cl-/HCO3- exchange) or inaccessibility of plasma HCO3- to red blood cell or pulmonary carbonic anhydrase. The present study characterized the contribution of erythrocyte anion exchange and pulmonary and erythrocyte carbonic anhydrase to CO2 excretion and, hence, to postcapillary CO2-HCO3--H+ equilibration in blood-perfused turtle (Pseudemys scripta) lungs. Turtle lungs perfused in situ with red cell suspensions containing inhibitors of erythrocyte anion exchange and/or pulmonary and red cell carbonic anhydrase produced significant postcapillary blood PCO2 and pH disequilibria, while no disequilibria were measured when lungs were perfused with control red cell suspensions. Erythrocyte anion exchange and pulmonary intravascular carbonic anhydrase contributed 11 % and 9 %, respectively, to CO2 excretion during single-pass perfusion, whereas red cell and pulmonary carbonic anhydrase contributed 32 % to the measured CO2 excretion. The lack of a measurable PCO2 disequilibrium during perfusion with control erythrocyte suspensions in this study suggests that alternative mechanisms may be responsible for the arterial-lung PCO2 disequilibrium measured during breathing or diving episodes in turtles.

Biochemical, histological, and inhibitor studies of membrane carbonic anhydrase in frog gastric acid secretion

2001 ◽  
Vol 281 (1) ◽  
pp. G61-G68 ◽  
Author(s):  
Erik R. Swenson ◽  
Timothy W. Tewson ◽  
Per J. Wistrand ◽  
Yvonne Ridderstrale ◽  
Chingkuang Tu
Keyword(s):  
Carbonic Anhydrase ◽  
Acid Secretion ◽  
Molecular Mass ◽  
Gastric Acid Secretion ◽  
Gastric Acid ◽  
Before And After ◽  
Capillary Endothelial Cells ◽  
Membrane Bound ◽  
Acid Inactivation ◽  
Mucosal Side

Gastric acid secretion is dependent on carbonic anhydrase (CA). To define the role of membrane-bound CA, we used biochemical, histochemical, and pharmacological approaches in the frog ( Rana pipiens). CA activity and inhibition by membrane-permeant and -impermeant agents were studied in stomach homogenates and microsomal fractions. H+secretion in the histamine-stimulated isolated mucosa was measured before and after mucosal addition of a permeant CA inhibitor (methazolamide) and before and after mucosal or serosal addition of two impermeant CA inhibitors of differing molecular mass: a 3,500-kDa polymer linked to aminobenzolamide and p-fluorobenzyl-aminobenzolamide (molecular mass, 454 kDa). Total CA activity of frog gastric mucosa is 2,280 U/g, of which 10% is due to membrane-bound CA. Membrane-bound CA retains detectable activity below pH 4. Histochemically, there is membrane-associated CA in surface epithelial, oxynticopeptic, and capillary endothelial cells. Methazolamide reduced H+secretion by 100%, whereas the two impermeant inhibitors equally blocked secretion by 40% when applied to the mucosal side and by 55% when applied to the serosal side. The presence of membrane-bound CA in frog oxynticopeptic cells and its relative resistance to acid inactivation and inhibition by impermeant inhibitors demonstrate that it subserves acid secretion at both the apical and basolateral sides.

scholarly journals Localization of xanthine dehydrogenase mRNA in horse skeletal muscle by in situ hybridization with digoxigenin-labelled probe

1993 ◽  
Vol 292 (3) ◽  
pp. 639-641 ◽  
Author(s):  
L A Räsänen ◽  
U Karvonen ◽  
A R Pösö
Keyword(s):  
Skeletal Muscle ◽  
Endothelial Cells ◽  
In Situ Hybridization ◽  
Northern Blot ◽  
Cdna Sequence ◽  
Muscle Cells ◽  
Xanthine Dehydrogenase ◽  
Capillary Endothelial Cells

In situ hybridization was used to localize xanthine dehydrogenase (XDH) mRNA in horse skeletal muscle. Capillary endothelial cells were found to express XDH, but muscle cells did not give any signal. The digoxigenin-labelled probe was produced by PCR with primers based on the cDNA sequence of mouse XDH and horse lung cDNAs. A 4.3 kb mRNA was detected in a Northern blot.

Effects of dextran-bound inhibitors on carbonic anhydrase activity in isolated rat lungs

1986 ◽  
Vol 61 (5) ◽  
pp. 1849-1856 ◽  
Author(s):  
T. A. Heming ◽  
C. Geers ◽  
G. Gros ◽  
A. Bidani ◽  
E. D. Crandall
Keyword(s):  
Molecular Weight ◽  
Carbonic Anhydrase ◽  
Time Course ◽  
Co2 Concentration ◽  
Carbonic Anhydrase Activity ◽  
Low Molecular Weight ◽  
Co2 Diffusion ◽  
Rat Lungs ◽  
Co2 Excretion ◽  
Isolated Rat

Effects of macromolecular Prontosil-dextran inhibitors (PD) on carbonic anhydrase (CA) activity in isolated rat lungs were studied. Isolated lungs were perfused with Krebs-Ringer bicarbonate (KRB) solutions containing no inhibitor, PD 100,000 (mol wt 100,000), PD 5,000 (mol wt 5,000), or low-molecular-weight inhibitors (Prontosil or acetazolamide). The time course of effluent perfusate pH equilibration was measured in a stop-flow pH electrode apparatus. Pulmonary CO2 excretion (Vco2) was monitored by continuously recording expired CO2 concentration. The lungs were ventilated with room air and perfused at 37 degrees C with KRB prebubbled with 5% CO2- 20% O2- 75% N2. The results obtained show that both the low-molecular-weight inhibitors and PD′s caused postcapillary pH disequilibria (delta pH) in effluent perfusate. However, only acetazolamide and Prontosil caused a reduction in Vco2. These results suggest that there is an intravascular CA, presumably associated with endothelial cell membranes, that is accessible to all inhibitors used and is responsible in part for equilibration of the CO2- HCO3- -H+ reactions in the perfusate but, under the conditions used, does not affect CO2 excretion; and there is an extravascular (possibly intracellular) CA that can be inhibited by low-molecular-weight inhibitors, is primarily responsible for enhanced CO2 transfer across the alveolar-capillary barrier (perhaps via facilitation of CO2 diffusion), and is in part responsible for pH equilibration.

scholarly journals Plasma-soluble marker for intraorgan regional flows

1983 ◽  
Vol 245 (4) ◽  
pp. H707-H712 ◽  
Author(s):  
S. E. Little ◽  
J. B. Bassingthwaighte
Keyword(s):  
Endothelial Cells ◽  
Coronary Artery ◽  
Reuptake Inhibitor ◽  
Plasma Flow ◽  
Plasma Flows ◽  
Tissue Concentrations ◽  
Norepinephrine Reuptake Inhibitor ◽  
Capillary Endothelial Cells ◽  
Norepinephrine Reuptake

Measurement of regional plasma flow is needed to quantitate the delivery of substrates and drugs to cells. For estimating regional plasma flows an ideal deposition marker should be 100% extracted during transorgan passage and retained until local tissue concentrations can be measured. To escape quickly, the tracer must penetrate capillary endothelial cells rapidly. To be retained, it must bind or be transformed or accumulated by cells. Desmethylimipramine (DMI, mol wt 266.3), a norepinephrine reuptake inhibitor, is suitable. On injection of [3H]DMI and 131I-albumin simultaneously into the coronary artery inflow of isolated Ringer-perfused rabbit hearts at 37 degrees C, extractions were greater than 99% at plasma flows (Fs) up to 2.3 ml X g-1 X min-1 and greater than 94% with Fs up to 5.1. Retention at Fs less than 2.3 averaged 99.0 +/- 0.55% (SD, n = 6) at 0.5 min, 98.4 +/- 0.5% at 1 min, and 96.6 +/- 1.1% or greater than 95% at 3 min. Retentions were similar in two dog hearts in situ. With Fs greater than 3 ml X g-1 X min-1, there was greater escape, 4.2 +/- 2.7% at 1 min and 6.8 +/- 4.2% at 3 min. The fractional escape rates of loss at 2 min or more were about 1%/min at all flows, suggesting that the spatial profiles of deposition did not change thereafter. Thus DMI is nearly ideal as a "molecular microsphere."

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