Hemoperfusion, rate of oxygen consumption and redox levels of mitochondrial cytochrome c (+c1) in liver in situ of anesthetized rat measured by reflectance spectrophotometry

Tissue oximetry by diffusive reflective visible light spectroscopy: Comparison of algorithms and their robustness

It is essential to measure tissue oxygen saturation (StO₂ ) locally and in thin layers of tissue, for example, the bronchial mucosa, skin flaps and small bones. Visible light spectroscopy (VLS) with a shallow penetration depth is suitable method. Although several VLS algorithms have been developed and described, they have not yet been compared to each other. This hinders attempts to compare the clinical results obtained by different algorithms. To address this issue, we compared the algorithms of Harrison, Knoefel, Pittman-Duling, Sato and our OxyVLS oximeter, which applies the algorithm from Wodick and Lübbers, in a liquid phantom with optical properties of human tissue. We generally observed considerable differences between the algorithms, which were StO₂ dependent. Exceptions were OxyVLS and Sato, showing a high level of agreement with negligible StO₂ dependency. In spite of the considerable deviation between the other algorithms, the difference of StO₂ between them in clinically normal StO₂ was <10%. We did not observe any dependency of the algorithms on hemoglobin content of the phantom or temperature.

Central role of mitochondria in metabolic regulation of liver pathophysiology

Mitochondria play a central role in cellular energy metabolism. Oxidative phosphorylation occurs in the electron transport system of the inner mitochondrial membrane. Cytochrome aa3, b and c1 are encoded by mitochondrial DNA whereas cytochrome c is encoded by the nuclear gene, and these mitochondrial-DNA dependent cytochromes are decreased and electron transport at complex II, III and IV is disturbed in liver carcinomas and during carcinogenesis. The more the decreased cytochrome and oxidase activity are seen, the more significant is the increase in reactive oxygen species (ROS) production. ROS produced in mitochondria may be the main cause of nuclear-gene mutation in carcinogenesis. The mitochondrial dysfunction and overproduction of ROS plays a key role in progression of chronic hepatitis C and ethanol-induced liver injury. Ethanol also causes bacterial translocation in the intestine and the resulting lipopolysaccharides (LPS) activates Kupffer cells to produce pro-inflammatory cytokines. We suspect that non-alcoholic steatohepatitis (NASH) also is the result of increased ROS production in Kupffer cells and hepatocytes.

Diffuse reflectance spectrophotometry with visible light: comparison of four different methods in a tissue phantom

The purpose of the study was to compare algorithms of four methods (plus two modifications) for spectrophotometric haemoglobin saturation measurements. Comparison was made in tissue phantoms basically consisting of a phosphate buffer, Intralipid and blood, allowing samples to be taken for reference measurements. Three experimental series were made. In experiment A (eight phantoms) we used the Knoefel method and measured specific extinction coefficients with a reflection spectrophotometer. In experiment B (six phantoms) the fully oxygenated phantoms were gradually deoxygenated with baker's yeast, and simultaneous measurements were made with our spectrophotometer and with a reference oxymeter (ABL-605) in 3 min intervals. For each spectrophotometric measurement haemoglobin saturation was calculated with all algorithms and modifications, and compared with reference. In experiment C (11 phantoms) we evaluated the ability of a modification of the Knoefel method to measure haemoglobin concentration in absolute quantities using extinction coefficients from experiment A.Results. Experiment A: with the Knoefel method extinction coefficients (+/-SD) for oxyhaemoglobin at 553.04 and 573.75 nm were 1.117 (+/-0.0396) ODmM(-1) and 1.680 (+/- 0.0815) ODmM(-1), respectively, and for deoxyhaemoglobin 1.205 (+/- 0.0514) ODmM(-1) and 0.953 (+/-0.0487) ODmM(-1), respectively. Experiment B: high correlation with the reference was found in all methods (r = 0.94-0.97). However, agreement varied from evidently wrong in method 3 and the original method 4 (e.g. saturation above 160%) to high agreement in method 2 as well as the modifications of methods 1 and 4, where oxygen dissociation curves were close to the reference method. Experiment C: with the modified Knoefel method the mean haemoglobin concentration difference from reference was 8.3% and the correlation was high (r = 0.91). We conclude that method 2 and the modifications of 1 and 4 were superior to the others, but depended on known values in the same or similar phantoms. The original method 1 was independent of results from the tissue phantoms, but agreement was slightly poorer. Method 3 and the original method 4 could not be recommended. The ability of the modified method 1 to measure haemoglobin concentration is promising, but needs further development.

Usefulness of technetium-99m-galactosyl human serum albumin liver scintigraphy for assessment of severity of alcoholic hepatitis

We performed a liver scintigraphy using technetium-99m diethylene-triaminepentaacetic acid-galactosyl human serum albumin (99mTc-GSA), which images the functional liver mass through its binding to the specific receptor asialoglycoprotein receptor in patients with severe alcoholic hepatitis. Receptor index (LHL 15) was significantly lower in patients with alcoholic hepatitis, compared with controls with normal liver. Difference in the isotope uptake patterns between liver and heart varied according to the severity of liver disease, and made it possible to categorize 5 grades. Grading score could discriminate between the eventual outcome of the patients. Furthermore, single photon emission computed tomography showed the variable uptake patterns in the hepatic lobule, wherein there were no evident findings in macroscopic view at autopsy. The results of this study show the usefulness of 99mTc-GSA scintigraphy in the evaluation and prognosis of alcoholic hepatitis.

Color monitoring after replantation

The recognition of postmicrosurgical minute skin color changes is an important element in assessing vascular insufficiency that has traditionally relied on a skilled microsurgeon's subjective clinical impression. This study investigates the use of a color monitor for the objective quantitative evaluation of such skin color changes. Twenty-two replanted digits were monitored postmicrosurgically with a color meter while deep skin temperature recordings, an established method of postmicrosurgical monitoring, were taken simultaneously. The results showed that the digits' clinical courses, namely, "uneventful," "necrosis," "congestion," and "acute arterial obstruction," showed characteristic patterns of postmicrosurgical circulation that were reflected in skin color change measurements. The reliability of the color measurements was confirmed by the deep skin temperature recordings. This study suggests that skin color after microsurgery can be evaluated quantitatively with the proposed color monitoring system and that this system is useful for the diagnosis of postmicrosurgical vascular insufficiency.

Endogenous nitric oxide modulates ethanol-induced gastric mucosal injury in rats

BACKGROUND/AIMS

Endothelium-derived relaxing factor regulates vascular tone via vasodilation. The relative contribution of endogenous nitric oxide to the pathophysiology of ethanol-induced gastric mucosal microcirculatory disturbances was investigated in anesthetized rats.

METHODS

Macroscopic and microscopic gastric mucosal damage and gastric mucosal hemodynamics including blood flow and hemoglobin oxygen saturation (ISO2) were assessed by pretreatment with a specific NO synthase inhibitor, N omega-nitro-L-arginine (L-NNA), before and after intragastric administration of ethanol.

RESULTS

Pretreatment with L-NNA significantly increased macroscopic (7.7-fold) and microscopic damage caused by 30% ethanol. Concurrent administration of L-arginine, but not D-arginine, significantly reduced the increase in mucosal damage. Similar results were obtained with 60% ethanol. Pretreatment with L-NNA decreased both mucosal blood flow and ISO2 in the basal period and enhanced decreases in both mucosal blood flow (2.7-fold) and ISO2 (4.3-fold) induced by 30% ethanol compared with controls. Concurrent administration of L-arginine, but not D-arginine, significantly inhibited the effect of L-NNA on blood flow and ISO2 in the basal period as well as after intragastric administration of 30% ethanol.

CONCLUSIONS

Endogenous NO modulates ethanol-induced gastric mucosal injury through the regulation of gastric mucosal microcirculation.

Contribution of the mitochondrial compartment to the optical properties of the rat liver: a theoretical and practical approach

The purpose of this work was to analyze the contribution of the mitochondria to the optical properties, i.e., light absorption and scattering, of the blood-free rat liver. Firstly, a theoretical model of the reduced scattering coefficient of the liver was performed by using the Mie theory, the Rayleigh-Debye-Gans approximation, and the electron microscopy descriptions of the liver ultrastructure. Compared with the hepatocyte volume, the nucleus and the peroxisomes, the mitochondria compartment, accounting for 22% of the liver cell volume, seemed to be the predominant factor for the light scattering of the liver. Second, by using time-resolved spectroscopy and a sample substitution method, we have measured the absorption and reduced scattering coefficients of blood-free perfused rat livers, isolated hepatocyte suspensions, and isolated mitochondria suspensions. A subsequent extrapolation of the isolated mitochondria data to the in vivo mitochondrial content and a comparison with the whole liver measurements lead to the following conclusions: 1) the mitochondria account for about 50% of the liver absorption coefficient at 780 nm (mu a = 0.25 cm-1 extrapolated from isolated mitochondria vs. 0.53 +/- 0.05 cm-1 measured for the liver); and 2) the mitochondrial compartment is the primary factor for the light scattering in the rat liver (mu s' = 15.5 cm-1 extrapolated from the isolated mitochondria versus 15.9 +/- 2.4 cm-1 measured for the liver), demonstrating the relevancy of our preliminary theoretical study.

Endothelin-1 is involved in the pathogenesis of ischemia/reperfusion liver injury by hepatic microcirculatory disturbances

Hepatic microcirculatory perturbation is observed after ischemia/reperfusion. Endothelin-1, a potent vasoconstrictive peptide, is known to modulate local circulation. This study was designed to examine whether endothelin-1 participates in the mechanism of microcirculatory disturbance and damage of the liver after ischemia/reperfusion. Ischemia in the median and left lateral lobes of the liver was induced for 60 min; it was followed by reperfusion for 24 hr. In some rats, endothelin-1 antiserum or control serum without endothelin-1-blocking activity was administered intravenously just before reperfusion. Rats were divided into three groups: an ischemia/reperfusion group that was injected with control serum, an endothelin-1 antiserum-treated group and a sham-operated group. Endothelin-1 concentrations in blood collected from the suprahepatic vena cava were measured before and after ischemia/reperfusion by use of a sandwich enzyme immunoassay. Index of blood volume in regional hepatic tissue and index of blood oxygenation in regional hepatic tissue were assessed with an organ reflectance spectrophotometry system before and at 5 min and 1, 2, and 24 hr after reperfusion. The endothelin-1 concentration in the ischemia/reperfusion group started to rise immediately at onset of reperfusion from basal values around 1 pg/ml and reached a value of 5 to 6 pg/ml 5 min after reperfusion; it was maintained at significantly high levels during the reperfusion period compared with the sham-operated group. Hepatic microcirculatory disturbance indicated by lowered index of blood volume in regional hepatic tissue and index of blood oxygenation in regional hepatic tissue levels was observed in the early phase of reperfusion in the ischemia/reperfusion group.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in oxygen consumption in dog gingiva during induction of experimental periodontitis

The purpose of this study was to examine changes in oxygen consumption in dog gingiva during induction of experimental periodontitis. The disease was induced in adult mongrel dogs during a 16-week period by placement of silk ligatures around selected teeth. The oxygen consumption rate of gingival tissue was determined in vivo by a non-invasive technique, tissue reflectance spectrophotometry. Changes in such clinical parameters as gingival index, plaque index, pocket depth, attachment level, and gingival crevicular fluid flow indicated acute inflammatory responses during the first three weeks after ligation, followed by the appearance of chronic inflammation during the remaining 13 weeks. The oxygen consumption rate increased during the first seven days after ligation and stayed near the maximum level for 2-7 weeks; this was followed by a gradual decrease during the final nine weeks. These results suggest that gingival oxygen consumption increases rapidly with the increase of acute inflammation responses and then decreases slightly with the gradual development of chronic inflammation. Positive correlations were observed between the oxygen consumption rate and other clinical indices. Thus, the tissue reflectance spectrophotometry is a new, useful method for objective, quantitative, and non-invasive assessment of gingival oxygen consumption.

Hepatic tissue oxygenation as a predictive indicator of ischemia-reperfusion liver injury

The purpose of this study was to determine whether hepatic tissue oxygenation after ischemia-reperfusion procedures is an indicator for later liver injury. Partial ischemia in the liver was induced by ligating the left pedicles. Rats were divided into two groups according to duration of ischemia: group A (30-min ischemia) and group B (60-min ischemia). Indices of blood oxygenation and blood volume in regional hepatic tissue, serum ALT levels and histological appearance of livers were evaluated. Twenty-four hours after ischemia and reflow, all rats in group A were alive, whereas only 67% survived in group B. Blood-oxygenation index and blood-volume index in group A rats rebounded quickly after reperfusion. In group B, blood-oxygenation index and blood-volume index remained significantly lower than in group A after reperfusion. Serum ALT levels at 60 and 120 min after reperfusion in group B were significantly higher than those in group A. Blood-oxygenation index measured at 5 and 60 min of reperfusion showed significant correlation with serum ALT levels at 120 min of reperfusion. When the percentage recovery of blood-oxygenation index at 5 and 60 min after reperfusion was more than 75%, all rats survived. No obvious signs of hepatocellular degeneration were observed histologically 5 min after reperfusion; however, substantial hepatocellular degeneration had occurred at 120 min of reperfusion in groups A and B. These data indicate that a decline in hepatic tissue oxygenation during the early phase of reperfusion (even when no obvious hepatocellular degeneration has been observed) can be a predictor of subsequent liver injury and prognosis.

Effects of proton pump inhibitor on gastric mucosa hemodynamics and tissue oxygenation in anesthetized rats

Proton pump inhibitors have been reported to have a cytoprotective action in addition to the anti-secretory action of acid. The precise mechanism, however, remains obscure. In this study, the effects of proton pump inhibitors (omeprazole and NC-1300) on gastric mucosa hemodynamics and tissue oxygenation were investigated using organ reflectance spectrophotometry in a hemorrhagic shock-reperfusion model involving anesthetized rats. Neither drug affected gastric mucosa hemodynamics nor tissue oxygenation in the basal state before hemorrhage. During the hemorrhagic shock state, however, these drugs maintained tissue oxygenation and reduced ulcer formation, although they did not show a significant effect on gastric mucosa blood volume. The results suggest that both proton pump inhibitors have an anti-ulcer action by maintaining mucosal oxygenation in addition to the anti-secretory activity of acid.

Changes in hemoglobin concentration and oxygen saturation in human gingiva with decreasing inflammation

The purpose of this study was to determine if functional changes in the human gingival vasculature were reversible following the resolution of gingival inflammation. Ten patients with 40 inflamed gingival sites were evaluated before and 2 weeks after the completion of treatment. We determined the hemoglobin concentration and the oxygen saturation of hemoglobin at each site by tissue reflectance spectrophotometry. With the use of treatment including motivation, oral hygiene instruction, and scaling, clinical parameters such as the gingival and plaque indices, the Periotron score, and the probing depth were altered toward a healthier state. With the resolution of gingival inflammation, the increased hemoglobin concentration and decreased oxygen saturation in the inflamed gingiva were restored to normal levels. These findings suggest that reversible changes in the local hemoglobin concentration and oxygen saturation are associated with decreasing gingival inflammation in human subjects.

Ethanol-induced disturbance of hepatic microcirculation and hepatic hypoxia

The hypothesis was tested whether ingestion of ethanol might disturb the hepatic microcirculation with resulting hepatic hypoxia. Infusion of ethanol increased the portal pressure concentration-dependently in rat livers perfused with Krebs-Henseleit buffer at a constant flow rate (Emax = 11.5 cm H2O, EC50 = 90 mM). This increase in portal pressure was due to hepatic vasoconstriction, since it diminished in the presence of sodium nitroprusside, a direct acting vasodilator. The regional hepatic tissue hemoglobin concentration after perfusion with added erythrocyte suspension (hematocrit 1%), measured by tissue-reflectance spectrophotometry, was significantly diminished by the infusion of ethanol, indicating the impairment of the microcirculation of the superficial layer of the liver. When the absorption spectrum of the liver was examined by reflectance spectrophotometry, infusion of ethanol caused a parallel reduction of all the mitochondrial respiratory cytochromes in a concentration-dependent fashion, concomitant with the increase of portal pressure, indicating a marked reduction of oxygen concentration in superficial liver tissue. The reduction of the respiratory cytochromes was also associated with the decrease in oxygen consumption of the liver, indicating that the hepatic hypoxia was due to the reduction of oxygen delivery to hepatocytes rather than the increased oxygen consumption of the liver. The reduction of the respiratory cytochromes was correlated with the increase in portal pressure and was inhibited by sodium nitroprusside. These data indicate that the ethanol-induced hepatic vasoconstriction disturbs hepatic microcirculation, resulting in hepatic hypoxia and reduction of mitochondrial respiratory cytochromes.

Fiber optic reflectance spectrophotometry system for in vivo tissue diagnosis

Fiber optic probes for a small portable reflectance spectrophotometry system for noninvasive clinical diagnosis have been developed. A slender fiber optic probe, 3 m long, 2.4-mm diameter, which goes into the channel of a fiber optic endoscope, has been developed as the standard probe. To expand the availability and capability of this reflectance spectrophotometry system, some variations of the fiber optic probes were developed: contact sensor, pressure sensor, attachments for dental use, and a modified-shape probe head for continuous monitoring. The feasibility of these fiber optic probes was examined experimentally.

Hemoglobin concentration and oxygen saturation of clinically healthy and inflamed gingiva in human subjects

The hemoglobin concentration (Hb index) and oxygen saturation (apparent SO2) in human gingiva were estimated by tissue reflectance spectrophotometry (TRS). The gingiva had significantly lower Hb index and higher apparent SO2 than those in alveolar mucosa, but there was no difference in either parameter among different gingival areas. The reproducibility in repeated measurements was high for both Hb index and apparent SO2 in gingiva. In inflamed gingiva, Hb index was significantly higher than that in clinically healthy gingiva. A lower apparent SO2 was observed in inflamed gingiva. This suggests that the increase in blood supply is insufficient to meet the oxygen demand in inflamed gingiva. There were significant correlations between either the Hb index or the apparent SO2 and the clinical parameters of gingival inflammation such as gingival index, plaque index, Periotron score and probing depth. Thus, TRS may be clinically available to estimate the blood volume and oxygen saturation in inflamed gingiva.

Impaired oxygen utilization. A new mechanism for the hepatotoxicity of ethanol in sub-human primates

The role of oxygenation in the pathogenesis of alcoholic liver injury was investigated in six baboons fed alcohol chronically and in six pair-fed controls. All animals fed alcohol developed fatty liver with, in addition, fibrosis in three. No evidence for hypoxia was found, both in the basal state and after ethanol at moderate (30 mM) or high (55 mM) levels, as shown by unchanged or even increased hepatic venous partial pressure of O2 and O2 saturation of hemoglobin in the tissue. In controls, ethanol administration resulted in enhanced O2 consumption (offset by a commitant increase in splanchnic blood flow), whereas in alcohol fed animals, there was no increase. At the moderate ethanol dose, the flow-independent O2 extraction, measured by reflectance spectroscopy on the liver surface, tended to increase in control animals only, whereas a significant decrease was observed after the high ethanol dose in the alcohol-treated baboons. This was associated with a marked shift in the mitochondrial redox level in the alcohol-fed (but not in control) baboons, with striking rises in splanchnic output of glutamic dehydrogenase and acetaldehyde, reflecting mitochondrial injury. Increased acetaldehyde, in turn, may aggravate the mitochondrial damage and exacerbate defective O2 utilization. Thus impaired O2 consumption rather than lack of O2 supply characterizes liver injury produced by high ethanol levels in baboons fed alcohol chronically.

Characterization of hepatic hemodynamics in cirrhotics and non-cirrhotics. Effect of glucagon infusion

The effect of glucagon on hepatic regional hemodynamics was investigated in patients with chronic liver disease during peritoneoscopy with reflectance spectrophotometry. When glucagon was infused intravenously in patients with a non-cirrhotic liver, the regional hepatic tissue oxygen consumption, as estimated spectrophotometrically, increased significantly, whereas the index of hepatic tissue blood volume did not change appreciably, and consequently, the oxygen saturation of hemoglobin in the hepatic tissue blood decreased. In contrast, the administration of glucagon in patients with liver cirrhosis resulted in a significant increase in the index of hepatic tissue blood volume and produced a minor increase in hepatic tissue oxygen consumption. The oxygen saturation of hepatic blood hemoglobin tended to increase in the cirrhotics. The result suggests the presence of functional vasoconstriction at the presinusoidal and/or sinusoidal vessels in the cirrhotic liver, possibly due to a decreased vasomotor activity and/or an abnormal regulatory function of vasoactive substances, which are released by glucagon.

Effect of cigarette smoking on the gastric mucosal blood volume index and hemoglobin oxygenation in man

The acute effect of cigarette smoking on the gastric mucosal blood volume index and the oxygen saturation of hemoglobin (SO2) in the gastric mucosa was investigated in 12 young male volunteers using reflectance spectrophotometry during endoscopy. Six of these volunteers were habitual smokers who had smoked more than 20 cigarettes a day for more than five years. The others were non-habitual smokers who smoked less than 20 cigarettes a year. The indices of mucosal blood volume and the mucosal blood SO2 level were calculated from the spectra obtained at the lesser curvature of the lower corpus of the stomach before and after cigarette smoking. The indices of mucosal blood volume and mucosal blood SO2 decreased significantly after one to three puffs of cigarette smoking in all subjects as compared to the value before smoking, and the degree of decrease in these parameters was significantly greater in the non-habitual smokers than in the habitual smokers. These results suggest that only one to three puffs of cigarette smoking causes a decrease in the mucosal blood volume and the mucosal blood SO2 which might be related to weakening of mucosal defensive factors.

Haemoglobin concentration and oxygen saturation in dog gingiva with experimentally induced periodontitis

The index of haemoglobin concentration (Hb index) and apparent oxygen saturation (apparent SO2) were determined by a new, non-invasive method, tissue reflectance spectrophotometry. The Hb index was positively correlated with the haemoglobin concentration. The relationship between the apparent SO2 and oxygen partial pressure was a sigmoid curve resembling the haemoglobin oxygen dissociation curve. The Hb index and the apparent SO2 were monitored continuously by tissue reflectance spectrophotometry during the induction of experimental periodontitis with silk ligatures. The Hb index increased rapidly during the first 7 days after ligation and then decreased gradually during the remaining period. The apparent SO2 decreased during the first 7 days but gradually rose during the final 9 weeks. The maximum level of the deoxyhaemoglobin concentration after ligation was elevated about two times over that found before ligation, whereas the increase in oxyhaemoglobin concentration was relatively small. These results suggest that the oxygen supply to inflamed gingiva may increase to some extent, but not sufficiently to compensate for the increased oxygen consumption.

Clinical application of tissue reflectance spectrophotometry to periodontal disease

Rapid, accurate, and non-invasive measurements of hemodynamics and oxygen utilization in gingiva are clinically important in evaluation of the severity of the inflammatory response in periodontal disease. In the present study, tissue reflectance spectrophotometry was used to examine gingiva in vivo to estimate hemoglobin concentration (Hb index) and the oxygen saturation level of hemoglobin in gingiva (HbSO2 index). Reflectance spectrophotometry was also used to examine these parameters in experimental periodontitis in dogs, and in patients with periodontal disease.

Both in vitro and in vivo experiments confirmed that the Hb index was positively correlated with hemoglobin concentration in gingival tissue. The relationship between the HbSO2 index and PO2 in gingiva was a sigmoid curve resembling the hemoglobin-oxygen dissociation curve. In rapidly advancing periodontitis resulting from ligature placement in dogs, the Hb index was significantly enhanced, but the HbSO2 index was reduced. This reduction corresponded to increases in gingival inflammation during the experiments. Furthermore, in humans, the Hb index was significantly higher in inflamed gingiva than in clinically healthy gingiva. A lower HbSO2 index was also found in inflamed gingiva. These findings are consistent with congested blood vessels, impaired venous return, and localized hypoxia in inflamed gingival tissue.

Tissue reflectance spectrophotometry is clinically useful in estimating blood volume and oxygen saturation in diseased gingiva.

Effect of hepatic blood oxygenation on bile secretion in rats

The effect of hepatic hemodynamics and hepatic tissue blood oxygenation on bile flow was studied in anesthetized rats by reflectance spectrophotometry. The hepatic hemodynamics and blood oxygenation were assessed by reflectance spectrophotometry. The hepatic ischemia was induced by partial ligation of portal vein and hepatic hypoxia was induced by inhalation of low concentration of oxygen. 1. The ischemia decreased hepatic blood volume index and hepatic blood oxygenation, and diminished bile flow. 2. Respiratory hypoxia suppressed hepatic oxygenation with minimal change of hepatic blood volume, and it also reduced the bile flow. 3. Bile flow was related hyperbolically with hepatic oxygenation and its dependency in hepatic ischemia and respiratory hepatic blood hypoxia identical. It is concluded that the hepatic tissue blood oxygenation affects hepatic energy metabolism, thus affecting the bile secretion.

In vivo estimation of oxygen saturation of hemoglobin in hepatic lobules in rats

We developed a system for the in vivo estimation of oxygen saturation of hemoglobin in the sinusoidal blood of periportal and pericentral regions of hepatic lobules in rats. There was a marked heterogeneity in blood oxygenation and oxygen gradients within hepatic lobules. The sinusoidal blood oxygenation was reduced in some pericentral regions within hepatic lobules following acute ethanol ingestion, suggesting an occurrence of perivenular hypoxia in the liver after acute ethanol consumption.

Reflectance spectrophotometric measurement of in vivo local oxygen consumption in the cerebral cortex

A simple method was developed to measure in vivo local oxygen consumption quantitatively in the brain cortex. Reflectance spectra of tissue hemoglobin at the brain's surface were measured for assessment of both local tissue hemoglobin content and its oxygen saturation. Local oxygen consumption was calculated from the spectral changes of tissue hemoglobin during complete cessation of blood flow by compression of the cortical surface in the suprasylvian gyrus with the tip of an optic probe. This procedure was performed without any brain damage and only took approximately 5 s. The calculated local oxygen consumption during this short period of compression remained constant for a few seconds. Then, it decreased rapidly, although the local tissue hemoglobin was not completely deoxygenated. The value of local cerebral oxygen consumption obtained by this method was 3.02 +/- 0.61 mL O2/100 g brain/min; it was not influenced by the change in systemic blood pressure. The effect of pentobarbital on cerebral oxygen consumption was also studied. At the stage of burst and suppression on electrocorticogram, cerebral oxygen consumption decreased significantly (p less than 0.001) to 1.03 +/- 0.07 mL O2/100 g brain/min.

Oxygen and substrate dependence of hepatic cellular respiration: sinusoidal oxygen gradient and effects of ethanol in isolated perfused liver and hepatocytes

The oxygen dependence of hepatic cellular respiration was studied by employing simultaneous organ spectrophotometry of cytochromes and hemoglobin, the latter used as an intrasinusoidal optical oxygen probe. The Km of cytochrome aa3 for oxygen was found to be 6.8 microM in the isolated perfused liver and 0.3 microM in suspensions of isolated hepatocytes. The results indicate that the sinusoid-to-cell pO2 gradient is about 5 torr. Optical determination of the average effective pO2 indicates that the axial sinusoidal O2 profile does not conform to zero-order O2 uptake in the liver. Because of extensive NAD+ reduction, ethanol increases the thermodynamic driving force of oxidative phosphorylation, and it also increased the oxygen consumption in both the perfused liver and the hepatocyte suspension, but had no effect on the grade of steady-state cytochrome aa3 reduction, the cellular energy state [ATP]/[ADP].[Pi], or the Km of cytochrome aa3 for oxygen. The results indicate that hepatic energy metabolism is oxygen independent at very low O2 concentrations, but that the sinusoidal axial O2 concentration is anomalous, probably due to the spatial arrangement of the metabolizing systems.

Misoprostol-induced changes in gastric mucosal hemodynamics. A double-blind parallel study in human volunteers

The effects of misoprostol on human gastric mucosal hemodynamics were examined in a double-blind, placebo-controlled, parallel study in 12 healthy male volunteers. Six subjects received 200 micrograms of misoprostol and six received placebo. The index of mucosal blood volume and mucosal blood hemoglobin oxygen saturation (Hb-SO2) were measured at 20 locations in the stomach using reflectance spectrophotometry during endoscopy prior to and after administration of the study drug. Mucosal blood volume index increased by approximately 10 to 25 percent throughout the stomach without a significant change in mucosal Hb-SO2 following treatment with misoprostol. The increase in mucosal blood volume index was statistically significant for 16 of the 20 locations (p less than or equal to 0.05). Placebo produced no significant change in mucosal blood volume and mucosal Hb-SO2. These findings suggest that misoprostol may have the potential effect of accelerating gastric ulcer healing by improving gastric mucosal hemodynamics, in addition to its gastric acid antisecretory activity.

Endothelium-dependent increases in rat gastric mucosal hemodynamics induced by acetylcholine and vagal stimulation

The role of vascular endothelial cells in the vagal control of hemodynamics was studied in rat gastric mucosa. Vagal stimulation and intra-arterial administration of acetylcholine and of papaverine increased hemoglobin (Hb) and oxygen saturation of hemoglobin (SO2) in the gastric mucosa. The increases induced by vagal stimulation were reduced but not abolished by atropine. The responses to acetylcholine and vagal stimulation were reduced by quinacrine, p-bromophenacyl bromide and nordihydroguaiaretic acid, while indomethacin had no effect. Intra-arterial infusion of collagenase removed the endothelial cells from submucosal vasculatures and depressed the increase in mucosal hemodynamics in response to acetylcholine and vagal stimulation. The response to papaverine was not depressed in rats treated with quinacrine or collagenase. These results suggest that the increase in gastric mucosal blood flow induced by acetylcholine or vagal stimulation is mediated by the endothelium-derived relaxing factor.

Estimated hepatic oxygen consumption in patients with chronic liver diseases as assessed by organ reflectance spectrophotometry

We investigated the estimated hepatic oxygen consumption by reflectance spectrophotometry during peritoneoscopy and the rate of in vitro oxygen consumption of liver slices obtained by liver biopsy using the oxygen electrode apparatus in patients with chronic liver diseases. The estimated hepatic oxygen consumption decreased concomitantly with the decrease in blood supply, expressed as the regional hepatic blood hemoglobin concentration, and it was significantly decreased in cirrhosis compared to chronic hepatitis. The estimated hepatic oxygen consumption also was significantly correlated with the serum albumin level, 15-min retention rate of indocyanine green, and prothrombin time. There was no correlation between the estimated hepatic oxygen consumption calculated from the reflectance spectra and the rate of in vitro oxygen consumption measured by the oxygen electrode apparatus. Most cirrhotic liver slices had a respiratory rate comparable to that in chronic hepatitis. Thus, it is concluded that the reduction of estimated hepatic oxygen consumption in cirrhosis of the liver is mainly due to the reduction of oxygen supply secondary to the decrease of hepatic blood flow.

Hepatic microcirculation in Zucker fatty rats

We have developed a microscopic analyzing system for studying in vivo hepatic microcirculation, and measured the sinusoidal erythrocyte flow velocity simultaneously in the various sinusoids. With this system and organ reflectance spectrophotometry, the pathophysiological role of microcirculation and of energy metabolism in Zucker fatty rats were studied. The results were as follows: The erythrocyte flow velocity in the predominant sinusoids in the fatty rats was similar to that of the control rats, but the intersinusoidal erythrocyte flow was undetected in the fatty liver. Index of regional hepatic blood volume, regional hepatic blood flow and oxygen saturation of Hb decreased significantly in the fatty rats. The estimated in vivo oxygen consumption was not changed in the fatty liver. From these data, it is concluded that in Zucker fatty rats a marked fatty infiltration causes a decreased hepatic tissue blood flow and volume, but relatively homogeneous erythrocyte flow with an increased extraction of oxygen compensated the decreased vascular beds and maintained normal energy metabolism.

Hepatic hemodynamics and oxygen consumption in alcoholic fatty liver assessed by organ-reflectance spectrophotometry and the hydrogen clearance method

Hepatic blood flow and estimated hepatic oxygen consumption were studied in rats treated chronically with ethanol by organ-reflectance spectrophotometry and the hydrogen clearance method. In the withdrawal state from ethanol, the concentration of hemoglobin in the hepatic tissue (delta Er569-650), the estimated hepatic oxygen consumption (estimated VO2) and the regional liver blood flow decreased significantly in rats treated chronically with ethanol in comparison with their controls. On the other hand, there was no significant difference in the estimated oxygen saturation of the hepatic blood hemoglobin (estimated SO2) between both groups. That is, an increase in oxygen extraction, which was exhibited by a decrease in the estimated SO2, did not occur in rats treated chronically with ethanol in spite of a decrease in blood supply. Thus, in the withdrawal state from ethanol, both oxygen delivery to the liver and oxygen utilization in the liver were disturbed at the stage of alcoholic fatty liver.

Effect of alcohol ingestion on portal venous blood flow in healthy volunteers: comparison between the subjects with and without ALDH I isozyme

Effect of alcohol ingestion (25 g ethanol) on portal venous blood flow was investigated in healthy subjects using an ultrasonic pulsed doppler method. It was found that; (1) portal blood flow increased by 24% at 30 minutes and returned to the basal level at 60 minutes after alcohol ingestion; (2) there was no significant difference in the effect of alcohol ingestion on portal blood flow between the subjects with and without ALDH I isozyme; (3) blood ethanol levels correlated with portal blood flow at 30 minutes after alcohol ingestion, while this correlation was not observed at 60 minutes thereafter; and (4) blood acetaldehyde levels did not correlate with portal blood flow either at 30 minutes or at 60 minutes following alcohol ingestion. In conclusion, the portal blood flow increases following alcohol ingestion which is not associated with the increase in the blood acetaldehyde level.

Hepatic hemodynamics in alcoholic liver injuries assessed by reflectance spectrophotometry

We have investigated the hepatic hemodynamics by reflectance spectrophotometry in patients with alcoholic liver disease. The analysis of 32 cases has shown that the estimated regional hepatic tissue blood hemoglobin concentration, expressed as a difference in absorbance between 569 and 650 nm (delta Er569-650), decreased significantly with progress of fibrosis in the liver, suggesting the relative compression of the vascular compartment due to the progress of alcoholic liver disease. The estimated hepatic oxygen consumption also decreased with progress of fibrosis in the liver. The estimated hepatic oxygen consumption correlated positively with prothrombin time and serum albumin level, and negatively with the fifteen minute retention rate of indocyanine green. Thus, it is concluded that the imbalance between supply and utilization of oxygen in the liver may have an important role in the progress of alcoholic liver disease.

Oxygen supply to the liver in patients with alcoholic liver disease assessed by organ-reflectance spectrophotometry

In the present study we have investigated hepatic hemodynamics in patients with alcoholic liver disease using reflectance spectrophotometry and the hydrogen clearance method. Analysis of 38 cases has shown that estimated regional hepatic-tissue hemoglobin concentration, expressed as a difference in absorbance between 569 and 650 nm (delta Er569-650), decreased significantly with progress of fibrosis or fat accumulation in the liver. This suggests that the relative compression of the vascular compartment is due to the progress of alcoholic liver disease. Estimated hepatic hemoglobin concentration also correlated positively with prothrombin time, and negatively with serum gamma-globulin level and 15-min retention rate of indocyanine green. The difference in absorbance between 569 and 650 nm obtained by reflectance spectrophotometry was positively correlated with the regional hepatic blood flow as measured by the hydrogen clearance method. Thus, it is concluded that the estimated regional hepatic-tissue hemoglobin concentration decreases with progress of fibrosis and fat accumulation in the liver, and that this decreased oxygen supply to the liver may have an important role in the progress of alcoholic liver disease.

In situ monitoring of myocardial metabolism by laser fluorimetry: relevance of a test of local ischemia

We have developed a hypoxia test by local ischemia, to be performed with a special probe adapted to an in situ NADH laser fluorimeter. Local ischemia is produced by pressurization on the organ surface in an area of approximately 0.2 mm2. In order to assess the method on open-chest rat hearts (ten), we used the following protocol: local ischemia tests (three), global anoxia (100% N2 ventilation), superimposition of local ischemia to global anoxia, and local ischemia tests during the period just prior to death and immediately thereafter. Three different responses were observed: large amplitude of compensated fluorescence (Fo) increase, medium amplitude of Fo increase, and no Fo increase. These responses were related to the metabolic state prior to the test (States 3, 4, and 5 of Chance's nomenclature). We have thus demonstrated the possibility of very rapidly determining the in situ NADH degree of reduction, without a destructive assay. Such a parameter may be of great relevance in heart surgery, as it might allow detection of potentially harmful situations, thereby enabling early and appropriate treatment.

Hypermetabolic state and hypoxic liver damage

The concept of a hypermetabolic state to explain metabolic tolerance to ethanol grew from the recognition that the rate of alcohol metabolism is, in general, limited by the rate at which mitochondria can reoxidize reducing equivalents and thus by the rate at which oxygen can be consumed by the liver. This relationship appears to be most important in conditions in which the alcohol dehydrogenase (ADH)/QO2 ratio is high and is not in conflict with observations suggesting that ADH can, under certain conditions, constitute a rate-determining step for ethanol metabolism in rodents. Liver preparations from animals fed alcohol chronically, in which an increase in ethanol metabolism is shown, consume oxygen at higher rates. This effect, concerning which there is discrepancy among investigators, depends on the type of preparation. Thyroid hormones play a permissive role in the development of the hypermetabolic state, while increased circulating levels of these hormones are not required. Antithyroid drugs inhibit both metabolic tolerance in vivo and the hypermetabolic state. While the hypermetabolic state requires an increased ATP utilization in the form of an adenosine triphosphatase, or an inhibition of ATP synthesis, the different mechanisms proposed for such an effect do not quantitatively account for the increases in oxygen consumption. In humans and animals chronically exposed to ethanol, but withdrawn, oxygen tensions in blood leaving the liver are significantly reduced. In some situations, low oxygen tensions in zone 3 of the hepatic acinus can reach critical hypoxic levels and may lead to cell necrosis. Studies in which the effectiveness of propylthiouracil is tested in human alcoholic hepatitis are discussed.

Effect of acute and chronic ethanol consumption on hepatic tissue oxygen tension in rats

In vivo hepatic tissue oxygenation was investigated in chronically ethanol-treated rats using micro oxygen electrode and reflectance spectrophotometry. Effect of acute ethanol administration was also studied. Hepatic oxygen tension of rats treated with ethanol chronically (daily ethanol intake, 9-12 g/kg for 9 months) was very low as compared with that of normal rats, the decrease being comparable to that of rats treated with carbon tetrachloride. The hepatic oxygen tension in normal controls shortly after ethanol ingestion increased from basal level (median, 23 mmHg) to 40-70 mmHg, while in chronically ethanol-treated rats, the hepatic oxygen tension decreased transiently, followed by a gradual increase, but it still remained low. In CCl4-treated rats, the hepatic oxygen tension decreased further after the ethanol ingestion. It is concluded that chronic ethanol consumption in rats resulted in hepatic hypoxia with decreased liver blood flow and volume. Also acute ethanol administration does not induce hepatic hypoxia in normal rats, while in rats with injured liver it induces hypoxia.

Noninvasive assessment of microcirculation of living organs and tissues using laser

For studying microcirculation of intact tissues or organs, a new noninvasive, heat-transient method using laser photoexcitation is described. As a heating source an argon ion laser or R6G dye laser was used via a quartz fiber optic guide. Infrared radiation from heated tissue was detected by a thermography apparatus. After switching the laser irradiation on and off, a thermal transient curve of a model tissue, the skin, was biphasic: a component with a fast time constant and the other with a slow time constant. The temperature increases of both phases following laser irradiation were linear to the applied power from the laser onto the tissue. The temperature rises as a function of the wavelength of irradiated light have shown that the absorption of the light by tissue hemoglobin is a main heat-generation source. Furthermore, the temperature rises as a function of tissue blood volume and flow have shown that the component with a slow time constant is more related to the tissue hemoglobin concentration and tissue blood flow and heat conductivity. Thus, the analysis of heat-transient curves following laser irradiation gives information as to regional tissue blood volume, blood flow, and tissue heat conductivity.