Endothelial adenosine transporter characterization in perfused guinea pig hearts

2000 ◽  
Vol 279 (4) ◽  
pp. H1502-H1511 ◽  
Author(s):  
Lisa M. Schwartz ◽  
Thomas R. Bukowski ◽  
James D. Ploger ◽  
James B. Bassingthwaighte
Keyword(s):  
Guinea Pig ◽  
Surface Area ◽  
Cell Types ◽  
Maximal Velocity ◽  
Passive Transport ◽  
Multiple Indicator Dilution ◽  
Luminal Membrane ◽  
Permeability Surface ◽  
Multiple Indicator

Adenosine (Ado), a smooth muscle vasodilator and modulator of cardiac function, is taken up by many cell types via a saturable transporter, blockable by dipyridamole. To quantitate the influences of endothelial cells in governing the blood-tissue exchange of Ado and its concentration in the interstitial fluid, one must define the permeability-surface area products ( PS) for Ado via passive transport through interendothelial gaps [ PS g(Ado)] and across the endothelial cell luminal membrane ( PS ecl) in their normal in vivo setting. With the use of the multiple-indicator dilution (MID) technique in Krebs-Ringer perfused, isolated guinea pig hearts (preserving endothelial myocyte geometry) and by separating Ado metabolites by HPLC, we found permeability-surface area products for an extracellular solute, sucrose, via passive transport through interendothelial gaps [ PS g(Suc)] to be 1.9 ± 0.6 ml · g−1 · min−1( n = 16 MID curves in 4 hearts) and took PS g(Ado) to be 1.2 times PS g(Suc). MID curves were obtained with background nontracer Ado concentrations up to 800 μm, partially saturating the transporter and reducing its effective PS ecl for Ado. The estimated maximum value for PS ecl in the absence of background adenosine was 1.1 ± 0.1 ml · g−1 · min−1 [maximum rate of transporter conformational change to move the substrate from one side of the membrane to the other (maximal velocity; V max) times surface area of 125 ± 11 nmol · g−1 · min−1], and the Michaelis-Menten constant ( K m) was 114 ± 12 μM, where ± indicates 95% confidence limits. Physiologically, only high Ado release with hypoxia or ischemia will partially saturate the transporter.

scholarly journals Optical measurement of isolated canine lung filtration coefficients at normal hematocrits

1997 ◽  
Vol 83 (6) ◽  
pp. 1976-1985 ◽  
Author(s):  
Joseph W. Klaesner ◽  
N. Adrienne Pou ◽  
Richard E. Parker ◽  
Charlene Finney ◽  
Robert J. Roselli
Keyword(s):  
Surface Area ◽  
Optical Measurement ◽  
Venous Pressure ◽  
Gravimetric Method ◽  
Volume Changes ◽  
Multiple Indicator Dilution ◽  
Permeability Surface ◽  
Multiple Indicator ◽  
Area Product ◽  
Filter Cartridge

Klaesner, Joseph W., N. Adrienne Pou, Richard E. Parker, Charlene Finney, and Robert J. Roselli. Optical measurement of isolated canine lung filtration coefficients at normal hematocrits. J. Appl. Physiol. 83(6): 1976–1985, 1997.—In this study, lung filtration coefficient ( K fc) values were measured in eight isolated canine lung preparations at normal hematocrit values using three methods: gravimetric, blood-corrected gravimetric, and optical. The lungs were kept in zone 3 conditions and subjected to an average venous pressure increase of 10.24 ± 0.27 (SE) cmH2O. The resulting K fc(ml ⋅ min−1 ⋅ cmH2O−1 ⋅ 100 g dry lung wt−1) measured with the gravimetric technique was 0.420 ± 0.017, which was statistically different from the K fc measured by the blood-corrected gravimetric method (0.273 ± 0.018) or the product of the reflection coefficient (ςf) and K fc measured optically (0.272 ± 0.018). The optical method involved the use of a Cellco filter cartridge to separate red blood cells from plasma, which allowed measurement of the concentration of the tracer in plasma at normal hematocrits (34 ± 1.5). The permeability-surface area product was measured using radioactive multiple indicator-dilution methods before, during, and after venous pressure elevations. Results showed that the surface area of the lung did not change significantly during the measurement of K fc. These studies suggest that ςf K fccan be measured optically at normal hematocrits, that this measurement is not influenced by blood volume changes that occur during the measurement, and that the optical ςf K fcagrees with the K fc obtained via the blood-corrected gravimetric method.

Endothelial extraction of tracer water is independent of temperature in dog lungs

1986 ◽  
Vol 250 (6) ◽  
pp. H1017-H1021
Author(s):  
F. P. Chinard ◽  
W. O. Cua
Keyword(s):  
Surface Area ◽  
Evans Blue ◽  
Indicator Dilution ◽  
Appearance Time ◽  
Flow Rates ◽  
Multiple Indicator Dilution ◽  
Permeability Surface ◽  
Multiple Indicator ◽  
Dilution Experiments ◽  
Dependent Flow

Diffusion and viscosity-dependent flow rates generally decrease with decrease of temperature in biological systems. We have examined the extraction (Ec) of tracer water in isolated dog lungs perfused near 37 degrees C and near 15 degrees C with multiple-indicator dilution experiments. If Ec were barrier limited, Ec should be less at lower temperatures. Two runs at 37 degrees C were followed by two runs at 15 degrees C. Evans blue (T-1824) was used as vascular reference, and tritium oxide (THO) was used as water tracer. Values of Ec were based on the ratio of the areas under the two indicator curves from appearance time to time of peak of T-1824. Values for permeability-surface area (PS) products were calculated from the classical Crone relationship in 14 experiments with a total of 56 runs. Neither Ec nor PS decreased with temperature. Instead, modest but statistically significant increases were found. We conclude that the extraction of tracer water in these preparations is not barrier limited.

Effect of perfusate hematocrit on urea permeability-surface area in isolated dog lung

1986 ◽  
Vol 61 (4) ◽  
pp. 1383-1387 ◽  
Author(s):  
R. E. Parker ◽  
R. J. Roselli ◽  
F. R. Haselton ◽  
T. R. Harris
Keyword(s):  
Surface Area ◽  
Left Lung ◽  
Multiple Indicator Dilution ◽  
Urea Permeability ◽  
Permeability Surface ◽  
Wide Range ◽  
Multiple Indicator ◽  
Area Product ◽  
Erythrocyte Trapping ◽  
Reference Tracer

Seven dog lower left lung lobes were statically inflated and perfused at a constant rate for each lobe with a perfusate in which the hematocrit was altered over a wide range. The permeability-surface area of urea was calculated from multiple indicator dilution curves using two separate injectates for each hematocrit level. One injectate contained only 125I-albumin as the vascular reference tracer and the other contained both 51Cr-erythrocytes and 125I-albumin as the vascular reference tracers; both contained [14C]urea as the permeating tracer. The results strongly indicate that the phenomenon of “erythrocyte trapping” of urea does not affect the calculation of urea permeability-surface area product provided the appropriate albumin-erythrocyte composite reference tracer is utilized in its calculation.

scholarly journals A comparison of ascorbate and glucose transport in the heart

1985 ◽  
Vol 249 (1) ◽  
pp. H141-H149 ◽  
Author(s):  
J. B. Bassingthwaighte ◽  
J. T. Kuikka ◽  
I. S. Chan ◽  
T. Arts ◽  
R. S. Reneman
Keyword(s):  
Surface Area ◽  
Indicator Dilution ◽  
Cell Permeability ◽  
Intracellular Space ◽  
Molecular Weights ◽  
Multiple Indicator Dilution ◽  
Modeling Analysis ◽  
Permeability Surface ◽  
Spatially Distributed ◽  
Multiple Indicator

Multiple indicator-dilution experiments were done to compare the transcapillary exchange of tracer amounts of L-[14C]ascorbate and D-[3H]glucose (against an intravascular reference 131I-albumin) in Ringer-perfused (5 mM glucose) isolated rabbit hearts. The indicator-dilution curves for the two were virtually superimposed over the first 40-80 s. Estimates of the capillary permeability-surface area products, PSc, were the same, 2.3 +/- 0.7 (SD) ml X g-1 X min-1 (n = 18), in accord with the coincidence of their instantaneous extractions. The similarity of glucose and ascorbate permeabilities is explained by the similarity in molecular weights and passive diffusivity, their lipophobic nature, and the paucity of carrier-mediated endothelial transport for either molecule. The data were analyzed via a model composed of aggregates of spatially distributed capillary-tissue units (capillary blood, interstitium, myocytes) accounting for the heterogeneity of regional flows. The interstitial volumes in this preparation are enlarged, 0.30 +/- 0.04 ml/g. There is substantial entry into myocardial cells, the cell permeability-surface area products being approximately 2-3 ml X g-1 X min-1 for ascorbate and glucose. The estimated volumes of interstitial and intracellular space, 0.30 and 0.47 ml X g-1 X min-1, reflect interstitial edema and are very close to measured values, giving reassurance concerning the methods of modeling analysis.

Effect of flow and surface area on angiotensin-converting enzyme activity in rabbit lungs

1987 ◽  
Vol 62 (5) ◽  
pp. 2042-2050 ◽  
Author(s):  
R. Moalli ◽  
B. R. Pitt ◽  
C. N. Gillis
Keyword(s):  
Surface Area ◽  
Converting Enzyme ◽  
Perfusion Rate ◽  
Multiple Indicator Dilution ◽  
Multiple Indicator ◽  
Ace Activity ◽  
Isolated Lungs ◽  
Indicator Dilution Techniques

Pulmonary angtiotensin-converting enzyme (ACE) is located on the luminal surface of pulmonary microvasculature. Multiple indicator-dilution techniques have been used to measure pulmonary ACE activity in vivo and in isolated lungs. These studies suggest that ACE activity is depressed in several forms of acute lung injury. Depression of ACE activity may reflect impaired substrate delivery to enzyme sites because of flow-related reduction of perfused surface area. To assess the role of altered microvascular flow and surface area in the measurement of ACE activity, we utilized similar techniques to estimate the apparent Km and Vmax of pulmonary ACE in isolated, Krebs-perfused rabbit lungs. Km is an estimate of the affinity of a synthetic ACE substrate, [3H]benzoyl-phenyl-alanyl-alanyl-proline ([3H]BPAP), for ACE and should not be influenced by the rate of substrate delivery to luminal enzyme sites. Conversely, Vmax is an index of the number of ACE sites and should be influenced by perfusion changes that alter the number of perfused sites (recruitment or derecruitment). When isolated lungs were subjected to physiological maneuvers designed to increase or decrease perfused surface area, apparent Vmax increased or decreased respectively. Apparent Km was not altered by these maneuvers. Km and Vmax were independent of changes in perfusion rate when surface area was held constant. Thus these parameters should be useful in evaluating perfusion changes in normal and injured lungs.

Transcapillary exchange of molecular weight markers in the postglomerular circulation: application of a barrier-limited model

1982 ◽  
Vol 242 (5) ◽  
pp. F436-F446
Author(s):  
C. Trainor ◽  
M. Silverman
Keyword(s):  
Molecular Weight ◽  
Excluded Volume ◽  
Excluded Volume Effects ◽  
Multiple Indicator Dilution ◽  
Filtration Barrier ◽  
Transit Times ◽  
Multiple Indicator ◽  
Dilution Experiments ◽  
Volume Effects

The permselectivity of the postglomerular capillary wall was studied by performing pulse-injection multiple indicator-dilution experiments on dog kidneys in vivo, using simultaneous injection of T1824-labeled albumin (plasma reference), creatinine (extracellular reference), and one or two radioactively labeled indicators: raffinose (595 dalton), vitamin B12 (1,357 dalton), or inulin (approximately 5,000 dalton). The urine transit patterns superimposed for all these except albumin, suggesting equal permeability for these molecular weight markers at the level of the glomerular filtration barrier. But the renal vein mean transit times progressively decreased. Therefore, their apparent interstitial volumes of distribution decrease with increasing molecular weight. This could be due to several factors acting singly or in combination: reduced capillary permeability in the postglomerular microcirculation; restricted diffusion in the postglomerular interstitium; or excluded volume effects. Evidence suggested that the effect was due to a combination of permeability and exclusion volume effects. To assess the validity of this assumption, the barrier-limited model was compared with the experimental data. The results were analyzed (both hydropenic and mannitol-diuretic dogs) and best fits calculated using two independent parameters, permeability and excluded volume. For permeability (X10(-4) cm/s, mean +/- SD) the range of values was always greater than or equal to 15 for creatinine and raffinose, and greater than or equal to 12 for B12. The permeability for inulin was 6.9 +/- 1.4. When interstitial volume excluded was expressed as percentage of the volume available to creatine, the excluded volume was negligible for raffinose and B12 but 12 +/- 5% for inulin. During mannitol diuresis the permeability for creatinine and raffinose remained high, but the values tended to decrease for B12. The permeability of inulin decreased to 2.9 +/- 0.09. Mannitol diuresis increased the excluded volume of inulin but did not alter the creatinine, raffinose, or B12 value.

Endothelial extraction of tracer water varies with extravascular water in dog lungs

1987 ◽  
Vol 252 (2) ◽  
pp. H340-H348 ◽  
Author(s):  
F. P. Chinard ◽  
W. O. Cua
Keyword(s):  
Volume Of Distribution ◽  
Indicator Dilution ◽  
Lung Water ◽  
Limited Distribution ◽  
Multiple Indicator Dilution ◽  
Multiple Indicator ◽  
The Time Domain ◽  
Area Product ◽  
Extravascular Volume

In multiple indicator-dilution experiments, transvascular passage of a permeating indicator is conventionally derived from the up-slope separation of the curve of the permeating indicator from that of a vascular reference and is expressed as the extraction (Ec). Extraction may be limited by the barrier (barrier-limited distribution). It may be limited by the volume of distribution accessible to it; in the time domain of an indicator-dilution experiment, the passage to and distribution in the extravascular volume are rapid relative to the velocity of blood in the exchange vessels. We examine here the relations of the extraction of tracer water as tritium oxide (THO) [Ec(THO)] and of the extraction of tracer sodium as 22Na [Ec(22Na)] to extravascular lung water, delta V wev, by adding isotonic fluid to the gas phase of the lungs. The net convective transvascular passage of water is negligible relative to the transendothelial molecular exchange. In 10 experiments in vivo and in 10 experiments in isolated perfused lungs, Ec(THO) increases as delta V wev increases. Ec(22Na) and the permeability-surface area product (PS) for 22Na do not change as delta V wev increases. We conclude that the extraction of THO is determined mainly by the volume accessible to it (flow- or volume-limited distribution) and that the extraction of 22Na is determined mainly by the resistance of the endothelium (barrier-limited distribution). A diffusion limitation in the added alveolar fluid rather than a barrier limitation at the endothelium may moderate Ec(THO).

Hepatic uptake of hippurate: a multiple-indicator dilution, perfused rat liver study

1998 ◽  
Vol 274 (1) ◽  
pp. G10-G20 ◽  
Author(s):  
Tsutomu Yoshimura ◽  
Andreas J. Schwab ◽  
Lei Tao ◽  
Ford Barker ◽  
K. Sandy Pang
Keyword(s):  
Benzoic Acid ◽  
Rat Liver ◽  
Hepatic Uptake ◽  
Indicator Dilution ◽  
Monocarboxylate Transporter ◽  
Maximal Velocity ◽  
Perfused Rat Liver ◽  
Hepatic Transport ◽  
Multiple Indicator Dilution ◽  
Multiple Indicator

The hepatic transport of hippuric acid (HA), a glycine-conjugated metabolite of benzoic acid that exhibits only modest plasma albumin binding (binding association constant of 2.1 × 103M−1), was studied in the single-pass perfused rat liver (12 ml/min), using the multiple indicator dilution (MID) technique. The venous recovery of [3H]HA on portal venous injection of a MID dose containing a mixture of a set of noneliminated reference indicators and [3H]HA revealed a survival fraction of unity, corroborating the lack of disappearance of bulk HA from plasma. When the outflow recovery was fitted to the barrier-limited model of Goresky et al. (C. A. Goresky, G. G. Bach, and B. E. Nadeau. J. Clin. Invest. 52: 991–1009, 1973), the derived influx ( P in S ) and efflux ( P out S ) permeability-surface area products were found to be dependent on the concentration of HA (1–930 μM); P in S and P out S were ∼3.5 times the plasma flow rate at low HA concentration, but decreased with increasing HA concentration. All values, however, greatly exceeded the expected contribution from passive diffusion, because the equilibrium distribution ratio of chloroform to buffer for HA was extremely low (0.0001 at pH 7.4). The tissue equilibrium partition coefficient ( P in/ P out, or ratio of influx to efflux rate constants, k 1/ k −1) was less than unity and decreased with concentration. The optimized apparent Michaelis-Menten constant and maximal velocity were 182 ± 60 μM and 12 ± 4 nmol ⋅ s−1 ⋅ g−1, respectively, for influx and 390 ± 190 μM and 29 ± 13 nmol ⋅ s−1 ⋅ g−1, respectively, for efflux. In the presence ofl-lactate (20 mM), however, P in S for the uptake of HA (174 ± 3 μM) was reduced. Benzoic acid (10–873 μM) was also effective in reducing hepatic uptake of HA (5.3 ± 0.9 μM). These interactions suggest that MCT2, the monocarboxylate transporter that mediates the hepatic uptake of lactate and other monocarboxylic acids, may be involved in HA transport.

Mechanism of maleic acid-induced glucosuria in dog kidney

1976 ◽  
Vol 231 (4) ◽  
pp. 1024-1032 ◽  
Author(s):  
M Silverman ◽  
L Huang
Keyword(s):  
Brush Border ◽  
Maleic Acid ◽  
Brush Border Membrane ◽  
Multiple Indicator Dilution ◽  
Dog Kidney ◽  
Proximal Tubular ◽  
Multiple Indicator ◽  
Prior Administration

The multiple indicator-dilution technique in vivo and isolated brush-border membranes in vitro have been used to explore the mechanism of maleic acid-induced glucosuria in dog kidney. The interaction of D-glucose with the antiluminal membrane from the peritubular fluid surface is unaltered. It is demonstrated that alpha-methyl-D-glucoside (alpha MG) enters and exits from the proximal tubular cell only across the brush-border membrane. Then using alphaMG as a reference indicator, it is shown that maleic acid does not cause complete inhibition of D-glucose interaction with the antiluminal membrane from the cytoplasmic surface. The binding of [3H]phlorizin both in vivo and in vitro is not affected by prior administration of maleic acid, indicating that D-glucose interaction with the outside surface of the brush border is also not affected by maleic acid. The data are therefore consistent with the concept that maleic acid-induced glucosuria is due either to i) partial inhibition of D-glucose movement from cytoplasm across the antiluminal membrane into the blood, ii) stimulated movement back across the brush-border membrane into urine, or iii) a combination of the two effects.

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