Intracellular Water Content Research Articles

Studies on in vitro effect of free fatty acids on water content and osmotic fragility of rabbit (lepus cuniculus) erythrocytes

The effects of free fatty acids in the blood on osmotic fragility and water content of erythrocytes when combined with hyperthermia were investigated. The isotonic buffer, containing the fatty acid, was added to the erythrocyte suspension to a final concentration of 200μM/L. The samples were kept for one hour in an incubator at 37 °C or 42 °C. The osmotic fragility of erythrocytes was determined by coil planet centrifuge system and intracellular water content was measured by gasliquid chromatography. A high concentration of unsaturated fatty acid and hyperthermia caused the increase in intracellular water and the decrease in osmotic resistance of the red blood cells compared to saturated fatty acid and the control. The present experiment demonstrated that unsaturated fatty acid was one of the principal chemical and metabolic factors which caused sports anemia.

Enhanced Protection Against Peroxidation-Induced Mortality of Aortic Endothelial Cells by Ascorbic Acid-2-O-Phosphate Abundantly Accumulated in the Cell as the Dephosphorylated Form

Bovine aortic endothelial BAE-2 cells exposed to the peroxidizing agent, tert-butylhydroperoxide (t-BuOOH) or 2,4-nonadienal (NDE), suffered from disruption of cell membrane integrity and from reduction of mitochondrial dehydrogenase activity as assessed by fluorometry using ethidium homodimer and photometry using WST-1, respectively. The cells were protected from t-BuOOH-induced injury more markedly by L-ascorbic acid-2-O-phosphate (Asc2P) stably masked at the 2,3-enediol moiety, which is responsible for the antioxidant ability of L-ascorbic acid (Asc), than by Asc itself. In contrast, NDE-induced membrane disruption but not mitochondrial dysfunction was prevented by Asc2P, whereas Asc exhibited no prevention against both types of injury. The amount of intracellular Asc was 7.2– to 9.0-fold larger in Asc2P-administered BAE-2 cells, where the intact form Asc2P was not detected, than in Asc-administered cells as assessed by HPLC of cell extract with detection by coulometric ECD and W. During transmembrane influx into the cell, Asc2P was concentrated as highly as 70– to 90-fold relative to the extracellular Asc2P concentration, whereas Asc was 8-to 13-fold concentrated as estimated based on an intracellular water content of 0.59 pL/cell determined by [14C]PEG/gas chromatography. Thus, Asc2P but not Asc is highly concentrated in the aqueous phase of the cell after prompt dephosphorylation, and may thereby render the cell more resistant to t-BuOOH-peroxidation assumedly via scavenging of intracellular reactive oxygen species than to peroxidation with the less hydroplulic agent NDE.

A mechanism for regulatory volume decrease in cultured lens epithelial cells

PURPOSE. To identify mechanisms contributing to regulatory volume decrease in lens epithelial cells. METHODS. Cells of the lens epithelial cell line aTN4 were cultured in four-well culture dishes in Dulbecco's Modified Eagle Medium containing 10% fetal bovine serum. After confluence cell water space was determined by measuring the equilibrium distribution of 3-O-methylglucose. Potassium influx and efflux in isotonic and hypotonic solutions were measured using 86 rubidium (86 Rb) as tracer. Total cell potassium and sodium content were determined with atomic absorption spectroscopy. Protein content per well was assayed with a modified Lowry assay and flux data and ion concentrations were normalized per mg of protein. RESULTS. Lens epithelial cells responded to hypotonic solutions with rapid swelling followed by regulatory volume decrease (RVD). During swelling and subsequent volume decrease the unidirectional Rb efflux was increased proportionaly to the osmotic challenge. Rubidium efflux was highly sensitive to changes in extracellular osmolarity and responded with a measurable activation to changes of 12.5 mOsm. No changes in 86 Rb influx were observed with small changes (<20%) in osmolarity and only relatively small changes occurred with larger changes in osmolarity. The resulting net loss of 86 Rb and potassium (K +) was demonstrated by measuring the change of intracellular [K + ] in hypotonic solutions using atomic absorption spectroscopy. The K + -channel blockers quinine-HCl and BaCl 2 and the Cl - -channel blockers diphenyl-2-carboxylate (DPC) and 5-nitro-2-(3-phenyl propylamino) benzoic acid (NPPB) did not significantly affect the 86 Rb efflux induced by hypotonic solutions. However, [(dihydroindenyl)oxy]alkanoic acid (DIOA), reported to be a specific inhibitor of the K-Cl cotransporter, inhibited the activation of 86 Rb efflux. 86 Rb efflux could be activated in isosmotic solutions by the addition of 1 mM N-ethylmaleimide (NEM). This activation of Rb efflux could be prevented by the addition of 1 mM dithiothreitol and could be 90% blocked by DIOA. The activation of rubidium efflux by NEM led to a significant decrease of the intracellular water content. The volume regulatory changes in NEM and in hypotonic solutions could be inhibited in DIOA. CONCLUSIONS. The observations are consistent with the presence in lens epithelial cells of a K-Cl cotransporter serving as a mechanism for regulatory volume decrease.

Increased oxidative and delayed glycogenolytic ATP synthesis in exercising skeletal muscle of obese (insulin-resistant) Zucker rats.

1. To examine metabolic correlates of insulin resistance in skeletal muscle, we used 31P magnetic resonance spectroscopy to study glycogenolytic and oxidative ATP synthesis in leg muscle of lean and obese Zucker rats in vivo during 6 min sciatic nerve stimulation at 2 Hz. 2. The water content of resting muscle was reduced by 21 +/- 7% in obese (insulin-resistant) animals compared with lean animals, whereas the lipid content was increased by 140 +/- 70%. These results suggest that intracellular water content was reduced by 17% in obese animals. 3. During exercise, although twitch tensions were not significantly different in the two groups, rates of total ATP synthesis (expressed per litre of intracellular water) were 48 +/- 20% higher in obese animals, suggesting a 50 +/- 8% reduction in intrinsic "metabolic efficiency'. Changes in phosphocreatine and ADP concentration were significantly greater in obese animals than in lean animals, whereas changes in intracellular pH did not differ. 4. These results imply that oxidative ATP synthesis during exercise is activated earlier in obese animals than in lean animals. This difference was not fully accounted for by the greater increase in the concentration of the mitochondrial activating signal ADP. Neither the post-exercise recovery kinetics of phosphocreatine nor the muscle content of the mitochondrial marker enzyme citrate synthase was significantly different in the two groups. The increased oxidative ATP synthesis in exercise must therefore be due to altered kinetics of mitochondrial activation by signals other than ADP. 5. Thus, the insulin-resistant muscle of obese animals may compensate for its decreased efficiency (and consequent increased need for ATP) by increased reliance on oxidative ATP synthesis.

Amiodarone affects membrane water permeability properties of human erythrocytes and rat mitochondria

Dose-dependent water exchange times and intracellular water contents were measured by NMR (nuclear magnetic resonance) in erythrocytes and mitochondria interacted with the anti-anginal and anti-arrhytmic agent, amiodarone. Addition of the drug up to 26 μM yielded 80% enhancement of the water exchange rate in erythrocytes at 37°C and 41% enhancement at 22°C with 40% and 9%, respectively, increases in the intracellular water content. Similar enhancements were obtained in mitochondria at 22°C. The data suggests a somewhat higher affinity of amiodarone to mitochondrial than to erythrocyte membranes.

Effects of hypernatraemia in the central nervous system and its therapy in rats and rabbits.

1. We studied the effects of acute (1 or 4 h) and chronic (1 week) hypernatraemia (plasma [Na+], 170-190 mM) on brain histology, and brain water and solute contents in rats and rabbits. 2. In rabbits with acute hypernatraemia, there was significant loss of intracellular brain water, with increases in brain [Na+ + K+], amino acid concentration, and undetermined solute (idiogenic osmole). After 1 week of recovery, brain intracellular water content had returned to normal. 3. In hypernatraemic rats there was myelinolysis of brain white matter, with karyorrhexis and necrosis of neurons. 4. Hypernatraemic rabbits were treated with 77 mM NaCl (i.v.) to normalize plasma [Na+] over 4-24 h intervals. Therapy of either acute or chronic hypernatraemia resulted in significant brain oedema because brain osmolality failed to decrease at the same rate as plasma osmolality. 5. It is concluded that: (a) untreated hypernatraemia results in brain lesions demonstrating myelinolysis and cellular necrosis; (b) normalization of hypernatraemia over 4-24 h results in cerebral oedema, due primarily to failure of brain amino acids and idiogenic osmoles to dissipate as plasma [Na+] is decreased to normal.

Electron Probe X-Ray Microanalysis of Rabbit Ciliary Epithelium

Rabbit iris–ciliary bodies were preincubated in control and experimental Ringer's solutions before quick freezing, cryosectioning, dehydration and electron probe X-ray microanalysis. After preincubation in a baseline bicarbonate-free Cl -Ringer's solution, the ciliary epithelial intracellular Na +, K +and Cl -concentrations were estimated to be 15±3, 162±14 and 46±5mmolkg -1intracellular water, respectively. The water and elemental Na, K, Cl and P contents were similar in the non-pigmented (NPE) and pigmented (PE) ciliary epithelial cells. As expected, inhibition of the Na,K-exchange pump by preincubation with ouabain markedly increased the intracellular Na content, and markedly reduced the intracellular K content, verifying the validity of the experimental analysis. The Cl -channels of the NPE cells likely play a critical role in determining the rate of aqueous humor formation. Therefore, we have examined the effects of altering Cl -transport on the intracellular composition in this initial microprobe study of the ciliary epithelium. As expected, exposure to bicarbonate increased the intracellular Cl and water contents. Replacement of external Cl -by NO 3 -was twice as effective as replacement by gluconate in leaching Cl -out of the intracellular compartment. An unexpected finding was that NO 3 -replacement of internal Cl -substantially increased the intracellular Na and decreased the intracellular K content, possibly by stabilizing the Na,K-pump in the E 1P form and inhibiting enzyme activity.

Response of cell volume in Mytilus gill to acute salinity change.

The response of gill cell volume in Mytilus californianus and Mytilus trossolus (=edulis) to acute changes in salinity was assessed using three independent indicators: optical measurement of lateral cell height, measurement of intracellular water content using radiolabeled tracers and measurement of the contents of the major osmolytes of the gills. Optical measurements indicated significant variation in the response of individual lateral cells of M. californianus to acute low-salinity shock. Lateral cell height increased by approximately 20% shortly after abrupt exposure to 60% artificial sea water (ASW). Following this initial swelling, we estimate that a substantial regulatory volume decrease (RVD) was present in 25% of the trials. More commonly, however, an RVD was either absent or minimal: cell height remained elevated for at least 1 h, then returned to the control height when gills were re-exposed to 100% ASW. Changes in the combined water space of all cells in the gill, measured as the difference between total water space and extracellular space ([14C]polyethylene glycol space), indicated that cell volume regulation in the gill as an organ was also absent or minimal. Cell water space was 2.16 ml g-1 dry mass in isolated gills of M. californianus acclimated to 100% sea water in the laboratory and increased to 2.83 ml g-1 dry mass after a 6 min exposure to 60% ASW. Cell water space was still 2.81 ml g-1 dry mass after 1 h in 60% ASW and returned to 2.06 ml g-1 dry mass upon re-exposure to 100% ASW. Consistent with these observations, the gill contents of the principal cytoplasmic osmolytes (taurine, betaine and K+) were unchanged (approximately 450, 250 and 230 mu mol g-1 dry mass, respectively) following exposure of gills from 100% ASW-acclimated mussels to 60% ASW. A decrease in cell water space to 2.66 ml g-1 dry mass after 4 weeks of acclimation to 60% ASW corresponded with a 37% decrease in betaine content; taurine and K+ contents were unchanged. The changes in water space and solute content of gills from freshly collected M. californianus and M. trossolus were also consistent with the absence of volume regulation; cell water space remained elevated for at least 1 h after low-salinity exposure, and solute contents were unchanged after this period. We calculated the potential energetic cost of cell volume regulation for mussels exposed to 12 h of sinusoidal fluctuations between 100% and 50% sea water; solute uptake for full volume regulation in all tissues would cost a minimum of approximately 30% of the standard metabolic rate during the period of salinity increase. The routine absence of substantial cell volume regulation in Mytilus gill may reflect the potentially high energetic cost of volume regulation in the face of the large and frequent salinity fluctuations that are regularly encountered by estuarine bivalves.

Hematologic and body fluid changes during simulated high altitude exposure in naproxen-treated rats.

Arterial blood oxygen saturation, body fluid and hematological parameters were studied in control, naproxen (a prostaglandin synthesis inhibitor)-treated control, altitude-exposed, and naproxen-treated altitude-exposed rats after intermittent exposure of 8 h/d for 6 consecutive days to a simulated high altitude of 6,100 m (barometric pressure 349 +/- 3 mmHg). Arterial blood oxygen saturation was reduced in altitude-exposed rats, but increased significantly to near control level in naproxen-treated rats. On the other hand, 2,3-diphosphoglycerate in erythrocytes increased in altitude-exposed rats, but naproxen prevented this increase. The red blood cell count, hemoglobin concentration and hematocrit ratio were reduced significantly in drug-treated altitude-exposed rats when compared to the altitude-exposed group (without drug). Red cell mass was increased in the altitude-exposed group in comparison with control. Both red cell mass and mean corpuscular volume of altitude-exposed rats were shifted towards the control value when they were treated with naproxen. Drug-treated high altitude-exposure reduced the thiocyanate space, intracellular fluid volume and total body water content compared to drug-treated control rats. On the other hand, thiocyanate space and total body water content were increased significantly in drug-treated control rats in comparison with the control group.

Magnetization transfer in hemopoietic bone marrow examined by localized proton spectroscopy

The sensitivity of hemopoietic bone marrow to magnetization transfer is analyzed in 15 healthy volunteers and seven patients with different hematological disorders (inflammation, plasmacytoma, hemopoietic reconstitution after bone marrow transplantation). To obtain sufficient signal-to-noise ratio, a 90 degrees - 180 degrees - 180 degrees double spin echo (PRESS) single voxel spectroscopic method was combined with pulsed magnetization transfer. Several spectra were recorded from each volume element inside the vertebral marrow, alternately with and without prepulses for magnetization transfer. Water signals from marrow with increased content of extracellular water due to inflammation or edema revealed less magnetization transfer effects than marrow with increased intracellular water content due to high cellularity. The preliminary results show magnetization transfer to be a promising tool for the clinically important characterization of the water composition in red bone marrow.

Dosimetry and Standardization of Tritium in Russia

Specific features of metabolism of different classes of tritium compounds have been studied in experiments with rats and mice. The results indicated the value of intracellular content of water is by 15-40% less than the average content of water in the whole tissue. Protracted retention in lungs of particles of luminous compounds and Ti tritide inhalated or introduced into trachea was shown. So, the particles are assigned to class Y according to ICRP. Foreign lowmolecular organic tritium compounds are effectively excreted with urine. Biogenic tritium compounds are bound in tissues at synthesis of biopolymers in dependence on need of body in them. According to our experiments, 1 to 90 % of tritium is separated from all incorporated compounds into body water in the form of HTO. The obtained metabolic data along with results of new radiobiological experiments on mice for RBE and biogenic tritium compounds effectiveness were the basis for development and introduction in Russia of standards for insoluble and biogenic tritium compounds and separately - for labelled precursors of nucleic acids.

Modulation of Na(+)-H+ exchange by altered cell volume in perfused rat mandibular salivary gland.

1. Intracellular pH (pHi) was measured by spectrofluorometry in perfused mandibular salivary glands isolated from the rat and loaded with the pH-sensitive fluoroprobe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Cell volume changes were estimated from changes in intracellular water content measured by proton NMR spectroscopy. 2. Stimulation with 1 microM acetylcholine (ACh) led to a 15 +/- 2% decrease in cell volume. A transient decrease in pHi was followed by a sustained increase (0.17 +/- 0.03 pH units) that has previously been attributed to the upregulation of the Na(+)-H+ exchanger. 3. Increasing perfusate osmolarity by addition of 60 mM sucrose caused a 19 +/- 2% decrease in cell volume and a sustained increase in pHi (0.12 +/- 0.01 pH units) that was abolished by 1 mM amiloride. Acid loading experiments indicated that the increase in pHi was due to an alkaline shift in the pH dependence of the Na(+)-H+ exchanger. 4. A 20% reduction in perfusate osmolarity prevented the cell shrinkage normally associated with ACh stimulation and largely abolished the ACh-induced increase in pHi. 5. Steady-state Na(+)-H+ exchanger activity, estimated from the initial rate of change in pHi following addition of amiloride, increased 9-fold during stimulation with ACh. When cell shrinkage was prevented by simultaneous exposure to the hypotonic solution, the activity of the exchanger still increased 7-fold in response to ACh. 6. We conclude that, although cell shrinkage leads to upregulation of the Na(+)-H+ exchanger, this factor alone is insufficient to account for the marked increase in exchanger activity that follows muscarinic stimulation.

The square-wave approach to impedance measurement of brain tissue water dynamics

Electrical properties of living soft tissue have been used to analyze their structure and function. Presently, the ‘admittance locus’ method, with the sine-wave signal of changing frequeney, is the most informative continuous method for analyzing extraand intracellular water content in brain tissue. Using the square-wave signal in lieu of the sine-wave signal, we can avoid cumbersome and costly measurements and facilitate real-time data processing. An isolation-calibration device was developed for the present study in order to condition and stabilize electrical current through the brain cortex. This device was also used for impedance calibration before and after the experiments. We propose a simple algorithm for data analysis on the basis of equivalent circuit approach, which allows to develop a computer program for data processing. Preliminary experiments on rat brains were carried out with a 0.2–0.5 mm stainless-steel tetrapolar electrode system. These studies showed good linearity between stimulating currents ( I = 5–30 μA) through the external electrodes in the brain cortex and a drop in voltage which was measured by 2 inner electrodes. The results of the device and the program accuracy tests allow us to choose the optimal range for the working current. We can recommend this method for usage in animal experiments.

Increased Intracellular Potassium and Water Contents in Rat Heart after α‐1‐Adrenoceptor Stimulation

Potassium accumulation in rat heart after alpha-1-adrenoceptor stimulation has previously been reported from indirect measurements. Here we present data on intracellular potassium content measured directly in the heart. Isolated rat hearts perfused in a non-recirculating system were exposed to alpha-1-adrenoceptor stimulation (5 x 10(-5) mol/l phenylephrine in the presence of 10(-6) mol/l timolol). 14C-Sucrose was used to estimate the extracellular space. From heart homogenates intracellular potassium, magnesium and cellular water contents were determined and the ion concentrations calculated accordingly. The intracellular magnesium content remained unchanged during all experimental conditions. alpha-1-Adrenoceptor stimulation evoked an increase in potassium content by 9% (4, 14; 95% confidence interval (CI), P = 0.0006). Due to an observed increase in intracellular water by 17% (9, 26; 95% CI, P = 0.0006), the potassium concentration apparently decreased by 8% (0.3, 15; 95% CI, P = 0.04). During partial inhibition of the Na+/K(+)-ATPase by 10(-5) mol/l ouabain, there was an increase in potassium content by 5% (1, 9; 95% CI, P = 0.008). There was, however, no significant increase in intracellular water in this situation. Calculated intracellular potassium concentration showed accordingly a slight increase. The effects upon potassium and water both in the absence and presence of ouabain were eliminated by the alpha-1-adrenoceptor blocker prazosin (10(-6) mol/l). alpha-1-Adrenoceptor stimulation apparently increased cellular dry weight by 10% (2, 18; 95% CI, P = 0.02). Changes in translocation of potassium and water must be considered as part of the alpha-1-adrenergic heart effects.

Regulation of ion content and cell volume in isolated rat renal IMCD cells under hypertonic conditions.

The adaptive responses of cell volume and intracellular inorganic electrolytes to hypertonicity were investigated in isolated inner medullary collecting duct (IMCD) cells in vitro. Intracellular water and element content were determined simultaneously by a rapid centrifugation technique and electron-probe microanalysis, respectively. In the absence of adenosine 3',5'-cyclic monophosphate (cAMP), cells isolated at 600 mosM (268 mM NaCl) shrank in 900 mosM buffer (418 mM NaCl) within 100 s to 79 +/- 2% of the control volume and showed no regulatory volume increase (RVI). K+ content decreased steadily during the first 5 min to 18% below control. K+ concentration initially increased 25 +/- 2% above control and was normalized after 5 min to 144 +/- 10 mM (n = 6). Na+ and Cl- content increased slowly during the 60-min incubation period; at this point intracellular Na+ and Cl- concentrations were 97 +/- 6 and 59 +/- 7% (n = 6) above control levels (75 +/- 12 mM Na+ and 143 +/- 29 mM Cl-), respectively. In the presence of 10(-4) M 8-bromo-cAMP (8-BrcAMP; used as a substitute for antidiuretic hormone), IMCD cells showed RVI within 5 min. K+ content initially dropped 18 +/- 2% below control and recovered during the next 4 min but was 12 +/- 4% below control after 60 min. K+ concentration showed similar changes. Na+ and Cl- content increased to a larger extent than in the absence of 8-BrcAMP to 95 +/- 10% (Na+) and 47 +/- 6% (Cl-) above control after 60 min, whereas Na+ and Cl- concentrations were the same as without 8-BrcAMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous measurement of cell volume changes in perfused rat salivary glands by proton NMR.

Changes in intracellular and extracellular water content have been measured in perfused rat salivary glands by repetitive application of an inversion recovery (IR) pulse sequence. The relaxation reagent Gd-DTPA (10 mM) was included in the perfusate so that the intracellular and extracellular water proton signals could be distinguished by their different longitudinal relaxation times. Changes in water content in response to altered perfusion pressure and perfusate osmolarity were determined at 30-s intervals and indicated a clear separation of the intracellular and extracellular components. Using a modification of the IR pulse sequence, changes in intracellular water content were also measured at 6-s intervals. With this time resolution, differences in the rates of cell shrinkage in response to hyperosmotic perfusates and the secretomotor agonist acetylcholine were observed. The results suggest that this approach offers a relatively noninvasive method for studying cell volume regulation in intact, perfused tissues and organs.

The gene for human erythrocyte membrane protein band 7.2 (EPB72) maps to 9q33-q34 centromeric to the Philadelphia chromosome translocation breakpoint region.

Erthrocyte band 7.2b is a 31-kDa integral phosphoprotein absent from the erythrocytes of many patients with hereditary stomatocytosis (HSt). HSt is a heterogeneous group of disorders characterized by mouth-shaped erythrocyte morphology on peripheral blood smears. The clinical severity of HSt is variable; some patients experience hemolysis and anemia while others are asymptomatic. The red cell membranes of these patients usually exhibit abnormal permeability to sodium and potassium with resultant modification of intracellular water content. The band 7.2b protein has been purified and the cDNA cloned. The approved gene name and symbol are erythrocyte membrane protein band 7.2 and EPB72, respectively, as assigned by the Human Gene Nomenclature Committee. Using a human reticulocyte cDNA library as template, a 491-bp fragment corresponding to the 3' end of the coding region of the EPB72 cDNA was amplified. Three overlapping phase DNA clones were isolated using this probe. Four genomic DNA fragments of 2.0, 2.5, 4.5, and 5.0 kb, respectively, were isolated from these clones. To localize the EPB72 gene by fluorescence in situ hybridization, these genomic DNA fragments were labeled with biotin-11-dUTP and hybridized to metaphase chromosomes as described. Probes were preannealed to C[sub 0]t1-fractionated DNA to block repetitive sequences. Experiments were analyzed more » and digitally imaged using a cooled CCD camera. The probes, in combination, gave specific hybridization signals only in chromosome 9q. The gene for erythrocyte membrane protein 7.2 localized to 9q33-q34. « less

Characterization of water distribution in cell pellets using nonlabeled sodium thiosulfate as an interstitial space marker.

A procedure for determination of the intracellular water content of cells using a single, nonlabeled solute as an interstitial space marker is proposed. Sodium thiosulfate, which can be accurately assayed by a tritrimetric method, is found to be a good compound for this purpose. Cells are recovered both by filtration and centrifugation; the two techniques gave the same value for internal water, i.e., 650 mg of H2O/g of wet matter for Corynebacterium melassecola and 390 mg of H2O/g of wet matter for Penicillium roquefortii spores. The methodology of data handling, based on a regression technique, is also described. It allows one to obtain very reliable results and should be useful for any marker.

The Lack of Effect of Hemodilution, Myocardial Water Content, and Increased Coronary Artery Blood Flow on Integrated Myocardial Ultrasonic Backscatter in the Beating Canine Heart

The effects of coronary blood flow, tissue water content and hematocrit variation on the Integrated Myocardial Backscatter Rayleigh 5 (IBR5) and Fourier coefficient of amplitude modulation (FAM, an index of cardiac cycle-dependent variation in IBR5) were measured in five open chest dogs. Data were obtained at baseline, during adenosine infusion and after two hours of crystalloid hemodilution (Hct 15%). IBR5 of -46.4 +/- .94 dB at baseline did not change significantly during adenosine infusion (-45 +/- .85 dB) and after hemodilution (-46.4 +/- 2.0 dB). FAM at baseline was (4.0 +/- 1.0 dB) (3.8 +/- -1.0 dB) during adenosine infusion and after hemodilution (5.0 +/- 1.8 dB). Myocardial water content increased significantly (p < .05) from 78 +/- .20% at baseline to 80.7 +/- .17% after hemodilution. Coronary blood flow demonstrated a three-fold increase with adenosine and two-fold increase with hemodilution. Electronmicroscopy demonstrated an increase in intracellular and extracellular water content. In conclusion, IBR5 and FAM did not change significantly despite significant increases in coronary blood flow and myocardial water content. Myocardial cellular derangements seen with nonischemic cell swelling, increased blood flow and a fall in hematocrit are insufficient to affect integrated backscatter.

The Lack of Effect of Hemodilution, Myocardial Water Content, and Increased Coronary Artery Blood Flow on Integrated Myocardial Ultrasonic Backscatter in the Beating Canine Heart

The effects of coronary blood flow, tissue water content and hematocrit variation on the Integrated Myocardial Backscatter Rayleigh 5 (IBR5) and Fourier coefficient of amplitude modulation (FAM, an index of cardiac cylce-dependent variation in IBR5) were measured in five open chest dogs. Data were obtained at baseline, during adenosine infusion and after two hours of crystalloid hemodilution (Hct 15%). IBR5 of −46.4 ± .94 dB at baseline did not change significantly during adenosine infusion (−45 ± .85 dB) and after hemodilution (−46.4 ± 2.0 dB). FAM at baseline was (4.0 ± 1.0 dB) (3.8 ± -1.0 dB) during adenosine infusion and after hemodilution (5.0 ± 1.8 dB). Myocardial water content increased significantly (p〈.05) from 78 ± .20% at baseline to 80.7 ± .17% after hemodilution. Coronary blood flow demonstrated a three-fold increase with adenosine and two-fold increase with hemodilution. Electronmicroscopy demonstrated an increase in intracellular and extracellular water content. In conclusion, IBR5 and FAM did not change significantly despite significant increases in coronary blood flow and myocardial water content. Myocardial cellular derangements seen with nonischemic cell swelling, increased blood flow and a fall in hematocrit are insufficient to affect integrated backscatter.