Identification of G6PDH-active sinusoidal cells as Kupffer cells in the rat liver

Kupffer cells and pit cells are not effective in the defense against experimentally induced colon carcinoma metastasis in rat liver

The present study was performed to investigate processes involved in circumvention of the immune system by advanced stages of tumor growth in the liver. The efficacy of Kupffer cells and pit cells against cancer cells was tested in vivo in an experimental model of colon carcinoma metastasis in rat liver. Liver tumors were induced by administration of CC531 colon cancer cells into the vena portae. After 3 weeks, livers were obtained and partly fixed for electron microscopic procedures or frozen in liquid nitrogen for enzyme and immunohistochemistry at the light microscope level. The activation status of Kupffer cells was studied by expression of Ia-antigen (MHC class II) and by measurement of glucose-6-phosphate dehydrogenase (G6PDH) activity in the cells in situ as a measure of production of reactive oxygen species. Large numbers of Kupffer cells were found in liver parenchyma surrounding colon carcinomas when compared with levels in control livers, but these cells were not activated. Large numbers of activated monocytes and macrophages, cytotoxic T cells but only a few pit cells were found to be recruited to the boundary between liver parenchyma and tumors or their stroma. In those areas where cancer cells invaded liver parenchyma, only newly recruited macrophages and some Kupffer cells were present but few cytotoxic T cells or pit cells were found. The low activation status of Kupffer cells both in terms of production of reactive oxygen species and Ia-antigen expression and the absence of significant numbers of pit cells at tumor sites suggest that Kupffer cells and pit cells do not play a significant role in advanced stages of tumor growth. High levels of prostaglandin E2 were detected in the parenchyma of livers containing tumors and transforming growth factor beta was detected in the stroma of the tumors, therefore suggest that cytotoxicity of newly recruited monocytes, macrophages and cytotoxic T cells may be limited in these stages because of local production of these immunosuppressive factors.

Heterogeneity of kinetic parameters of enzymes in situ in rat liver lobules

In the present review, metabolic compartmentation in liver lobules is discussed as being dynamic and more complex than thus far assumed on the basis of numbers of mRNA or protein molecules or the capacity (zero-order activity) of enzymes. Isoenzyme distribution patterns and local kinetic parameters of enzymes may vary over the different zones of liver lobules. As a consequence, metabolic fluxes in vivo at physiological substrate concentrations may be completely different from those that are assumed on the basis of the number of molecules or the capacity of enzymes present in zones of liver lobules. For a more correct estimation of the levels of metabolic processes in the different compartments of liver tissue, local kinetic parameters and substrate concentrations have to be determined to calculate local metabolic fluxes. Direct measurements of metabolic fluxes in vivo with the use of noninvasive techniques is a promising alternative and the techniques will become increasingly important in future metabolic research.

Effects of partial hepatectomy, phenobarbital and 3-methylcholanthrene on kinetic parameters of glucose-6-phosphate and phosphogluconate dehydrogenase in situ in periportal, intermediate and pericentral zones of rat liver lobules

Glucose-6-phosphate dehydrogenase (G6PDH) and phosphogluconate dehydrogenase (PGDH) are heterogeneously distributed in liver lobules of female rats. The maximum activity of both enzymes is approximately twice higher in intermediate and pericentral zones than in periportal zones. Enzyme activities and their distribution patterns were manipulated by partial hepatectomy and treatment with phenobarbital (PB) or 3-methylcholanthrene (3-MC). Vmax values of G6PDH for glucose-6-phosphate decreased mainly in intermediate and pericentral zones after partial hepatectomy, whereas they increased after PB treatment. Vmax values of PGDH for phosphogluconate decreased after partial hepatectomy in both zones, whereas other treatments did not have any effect. The affinity of G6PDH for glucose-6-phosphate was similar in all zones and it was decreased 2-3 fold by PB and 3-MC treatment. The affinity of PGDH for phosphogluconate was 1.4-2.3 times lower in intermediate and pericentral zones than in periportal zones of all livers tested and was not affected by treatment. From these data it can be concluded that not only the maximum activity of enzymes may differ in periportal, intermediate and pericentral zones of the liver lobule but also the affinity of enzymes for their substrates. The implication of these findings is that metabolic flux rates as they occur in vivo in these different metabolic compartments may be significantly different from predictions on the basis of maximum enzyme activities as detected immunohistochemically, microchemically or cytophotometrically.

Quantitative comparison between the gel-film and polyvinyl alcohol methods for dehydrogenase histochemistry reveals different intercellular distribution patterns of glucose-6-phosphate and lactate dehydrogenases in mouse liver

The precise histochemical localization and quantification of the activity of soluble dehydrogenases in unfixed cryostat sections requires the use of tissue protectants. In this study, two protectants, polyvinyl alcohol (PVA) and agarose gel, were compared for assaying the activity of lactate dehydrogenase (LDH) and glucose-6-phosphate dehydrogenase (G6PDH) in normal female mouse liver. Quantification of enzyme activity was determined cytophotometrically in periportal (PP), pericentral (PC) and midzonal (MZ) areas. No coloured reaction product was present in PVA media after the incubation period. In contrast, the agarose gels appeared to be highly coloured after incubation. As a consequence, sections incubated with gel media were less intensely stained than those incubated in PVA-containing media. The specific G6PDH reaction (test minus control) yielded approximately 75% less formazan in sections incubated by the agarose gel method than with the PVA method. Further, the amount of formazan deposits attributable to G6PDH activity was highest in the midzonal and pericentral zones of the liver lobule with PVA media, and Kupffer cells could be discriminated easily because of their high G6PDH activity. Significant zonal differences or Kupffer cells could not be observed when agarose gel films were used for the detection of G6PDH activity. The LDH localization patterns appeared to be more uniform after incubation with both methods: no significant differences in specific test minus control reactions were seen between PP, PC and MZ. However, less formazan production (33%) was detected in sections incubated with agarose gels when compared with those incubated with PVA media.(ABSTRACT TRUNCATED AT 250 WORDS)

Intralobular heterogeneity of perisinusoidal stellate cells in porcine liver

The aim of the present investigation was to elucidate the intralobular heterogeneity of the perisinusoidal stellate cells (fat-storing cells, lipocytes) in the porcine liver. Their three-dimensional structure, desmin immunoreactivity and vitamin-A storage were studied by use of the Golgi silver, immunocytochemical and gold chloride methods. In order to locate the stellate cells, the hepatic lobules were divided into 10 zones. The stellate cells were readily identified in Golgi preparations by their striking dendritic appearance with branching processes encompassing the sinusoids. The stellate cells in the centrolobular zones were conspicuously dendritic with longer processes in comparison to those emitted by periportal elements. Such arborizations were studded with numerous thorn-like microprojections. Desmin immunoreaction in the periportal zones was stronger than that in the centrolobular zones. Vitamin-A storage in the stellate cells was well developed in zones 2-4, but reduced gradually toward the central region. The perisinusoidal stellate cells display marked heterogeneity in morphology and function based on their zonal location in the hepatic lobule.

Metabolic zonation of the liver: regulation and implications for liver function

Liver parenchyma shows a remarkable heterogeneity of the hepatocytes along the porto-central axis with respect to ultrastructure and enzyme activities resulting in different cellular functions within different zones of the liver lobuli. According to the concept of metabolic zonation, the spatial organization of the various metabolic pathways and functions forms the basis for the efficient adaptation of liver metabolism to the different nutritional requirements of the whole organism in different metabolic states. The present review summarizes current knowledge about this heterogeneity, its development and determination, as well as about its significance for the understanding of all aspects of liver function and pathology, especially of intermediary metabolism, biotransformation of drugs and zonal toxicity of hepatotoxins.

Fine structure and function of Kupffer cells

Kupffer cells are macrophages that are attached to the luminal surface or inserted in the endothelial lining of hepatic sinusoids. In this site, Kupffer cells play a key role in host defense by removing foreign, toxic and infective substances from the portal blood and by releasing beneficial mediators. Under some conditions, toxic and vasoactive substances also are released from Kupffer cells which are thought to play a role in a variety of liver diseases. Many of these activities may be modulated by the levels of gut derived endotoxin normally present in the portal blood. The ultrastructural aspects of Kupffer cell structure function in situ are best studied using perfused-fixed livers. In fixed livers, transmission and scanning electron microscopy reveal Kupffer cells during health to be irregular in shape with their exposed surfaces presenting numerous microvilli, filopodia, and lamellopodia. Long filopodia penetrate endothelial fenestrae to secure Kupffer cells to the sinusoid lining. Specific membrane invaginations known as worm-like bodies or vermiform processes are seen in the cytoplasm of Kupffer cells as are numerous endocytotic vesicles and lysosomes which vary in density, shape and size. Sometimes, annulate lamellae connected to the rough endoplasmic reticulum also are found. The principal endocytic mechanisms of Kupffer cells are phagocytosis of particulates and cells, and bristle-coated micropinocytosis for fluid-phase endocytosis of smaller substances. Many of these events are mediated by specific receptors. In some species, Kupffer cells can be distinguished from other sinusoidal lining cells and monocytes by specific cytoplasmic staining or monoclonal antibodies. Kupffer cells have been shown to be of monocytic origin as well as having the capacity for self-replication.

Biochemical microanalysis of alpha-glucosidase activity in preneoplastic and neoplastic hepatic lesions induced in rats by N-nitrosomorpholine

Preneoplastic and neoplastic hepatic lesions were induced in male Sprague-Dawley rats by oral administration of N-nitrosomorpholine (NNM) for 7 weeks at a concentration of 200 mg/l of drinking-water (stop model). Using a laser dissection technique and biochemical microanalysis, the activity of the lysosomal enzyme alpha-glucosidase was measured in glycogen storage foci emerging early, and in mixed or basophilic cell populations (foci and carcinomas) appearing later during hepatocarcinogenesis. In the liver tissue of normal appearance in both untreated controls and NNM-treated animals a slight gradient of alpha-glucosidase activity was observed leading from relatively high activities in zone 1 to lower activities in zone 3 of the liver lobule. In preneoplastic glycogen storage foci a considerable relative reduction in alpha-glucosidase activity was detected, suggesting that a decrease in the hydrolytic glycogen degradation contributes to the disturbance in phosphorylytic glycogen breakdown observed earlier in the majority of the glycogenotic foci. In contrast with glycogen storage foci, mixed and basophilic cell foci and particularly hepatocellular carcinomas showed a marked increase in alpha-glucosidase activity compared with that of normal liver tissue. The gradual enhancement in enzyme activity appeared to be closely related to the reduction in glycogen initially stored in excess during the later stages of hepatocarcinogenesis. The results support the concept that a fundamental shift in carbohydrate metabolism is characteristic of neoplastic transformation of hepatocytes.

Resident sinusoidal macrophages in the liver of the brown bullhead (Ictalurus nebulosus): an ultrastructural, functional and cytochemical study

Ultrastructural, functional, and cytochemical characteristics of resident sinusoidal macrophages (RSM) in brown bullhead (Ictalurus nebulosus) liver were examined. Following perfusion fixation of the hepatic vascular bed, light micrographs revealed RSM that possessed multiple elongate cytoplasmic processes and frequently contained erythrocytes in various stages of degradation. Following brief perfusion fixation, light microscope examination of vibratome sections of bullhead liver reacted for peroxidase revealed intensely positive RSM. By transmission electron microscopy, peroxidase activity was localized to the nuclear envelope and cytoplasmic granules of RSM and in endothelial and perisinusoidal fat-storing cells. In cryostat sections of fresh-frozen liver, glucose-6-phosphate dehydrogenase (G-6-PDH) was uniformly distributed over hepatocytes, whereas intensely positive punctate staining for G-6-PDH was localized over RSM. To test for phagocytosis by RSM, latex beads (0.81 micron) were injected into a tributary of the hepatic portal vein 2 min prior to perfusion fixation. Latex beads appeared either singly or in dense aggregates within RSM. Ultrastructurally, RSM were characterized by an irregularly shaped, eccentrically located nucleus, electron-dense vacuoles, small patches of granular endoplasmic reticulum, a well-developed Golgi apparatus, elongated mitochondria, desmosomes or desmosome-like densities that served as a source of attachment to endothelial cells, and a centriole with radiating microtubules. Invaginations of the plasma membrane (vermiform processes) characteristic of mammalian Kupffer cells were not observed in bullhead RSM. The results indicated a resident cell population of sinusoidal macrophages in the bullhead liver with properties that partially resembled mammalian Kupffer cells. These results are important for the identification of the normal resident cells in the bullhead liver.

Morphologic and histochemical analysis of the newt (Notophthalmus viridescens) liver

Architectural arrangement, ultrastructure, and selected histochemical properties of the newt (Notophthalmus viridescens) liver were examined. Although hematopoietic tissue (1-4 cells thick) invested the liver, direct vascular communication between this tissue and hepatic parenchyma was not observed. The liver was intensely positive when stained with Oil-red-O and periodic acid-Schiff reagent and connective tissue was limited to large vascular channels and the capsule. A distinctive polarity was observed in the hepatic vascular system when lobes were viewed in cross section. Dorsally, portal venules accompanied arterioles and branches of the biliary system, while tributaries of hepatic veins were observed ventrally. Following perfusion fixation, hepatocytes appeared as sheets of cells 1-5 cells thick; however, lobules as defined in adult mammalian liver were absent. Hepatocytes contained abundant smooth endoplasmic reticulum, mitochondria, electron-dense lysosomes, patches of granular endoplasmic reticulum, and lipid droplets. Continuous endothelial cells lined sinusoids and exhibited fenestrae organized into structures similar to sieve plates observed in mammalian liver. Variable numbers of melanin-containing macrophages and subendothelial macrophages were observed; however, Kupffer cells and lipid containing perisinusoidal fat-storing cells were not seen. Patterns of reaction product for glucose-6-phosphatase (G-6-Pase), glucose-6-phosphate dehydrogenase (G-6-PDH), and succinic dehydrogenase (SDH) were localized in the newt liver. All enzymes exhibited a uniform distribution pattern; however, small punctate regions of intensely positive G-6-PDH cells were noted within hepatic parenchyma. Cells comprising the hematopoietic tissue were intensely positive for G-6-Pase, G-6-PHD, and negative for SDH.

Functional units in rainbow trout (Salmo gairdneri) liver: I. Arrangement and histochemical properties of hepatocytes

The architectural arrangement and selected histochemical properties of hepatocytes in the rainbow trout (Salmo gairdneri Richardson) were examined. Light and transmission electron microscopic (TEM) examination following fixation by portal venous perfusion revealed a tubular arrangement of hepatocytes. Lobules, as defined in the adult mammal, were absent. Biliary epithelial cells associated with bile preductules and ductules were a prominent feature of trout liver. Patterns and location of reaction products for glucose-6-phosphatase (G-6-Pase), glucose-6-phosphate dehydrogenase (G-6-PDH), and magnesium-dependent adenosine triphosphatase (ATPase), enzymes preferentially distributed in mammalian liver, were demonstrated in trout liver. A slightly heavier staining pattern for G-6-Pase was seen around presumptive portal venules but all other enzyme reaction patterns were uniform throughout the liver parenchyma. Following ATPase localization, four sizes of biliary passageways (canaliculi, bile preductules, ductules, and ducts) were visualized. Maximum glycogen retention was achieved with freeze-drying and glycolmethacrylate embedding and with this method intense, uniform glycogen staining was observed in all areas of the liver. Companion TEM examinations revealed large depots of glycogen within hepatocytes. The results are important for interpretation and description of the effects of toxic/carcinogenic alteration on trout liver.

Histochemical and immunohistochemical localization of hexokinase isoenzymes in normal rat liver

Histochemical and immunohistochemical procedures have been used to examine the localization of three of the four hexokinase isoenzymes present in the liver of fed female Wistar rats. Distinctive distribution patterns were found for hexokinase type I and glucokinase but hexokinase type II was not detectable. Hexokinase type I was identified in sinusoidal cells and in bile duct epithelia, nerves and arteries in the portal triad. Glucokinase, the major isoenzyme, was confined to parenchymal cells where it was present in much higher amounts in perivenous compared with periportal hepatocytes. Staining within these two zones was not homogeneous and each had a mosaic appearance caused by the presence of a few hepatocytes containing little or no glucokinase amongst the majority of darkly stained cells in perivenous areas and a few darkly stained cells amongst the majority of unstained cells in periportal areas. Hence, hepatocytes in situ are a strikingly heterogeneous population of cells. Their metabolic status cannot be controlled simply by the differential supply of oxygen, substrates and hormones to different regions of the liver acini as proposed in the metabolic zonation model. Phenotypic differences may exist between cells within a given metabolic zone which influence their ability to respond to different environmental conditions.

Heterogeneity of endothelial cells of adult rat liver as resolved by sedimentation velocity and flow cytometry

Sinusoidal cells isolated from adult rat liver were fractionated by velocity sedimentation at 1 X g ( primarily on the basis of size) and the various cell fractions were further analysed by flow cytometry on the basis of forward and perpendicular light scattering and autofluorescence. Cell volume was also measured electronically using a Coulter counter. At least four enriched cell populations were resolved after velocity sedimentation. They corresponded to cells having a modal diameter of 6.5, 7.5, 9, and 11 microns, respectively. Transmission electron microscopy (TEM) analysis of the various cell populations revealed that the 7.5- and 9-microns cell fractions represented two distinct classes of endothelial cells while the 11-microns cells corresponded to Kupffer cells. The 6.5-microns cells were identified as lymphocytes. Fat-storing cells, identified by their autofluorescence and lipid content, were included in the Kupffer population. Further information about the nature of the two physically distinct endothelial cell populations was obtained by TEM. It demonstrated that the smaller endothelial cells possessed quantitatively and relatively less retracted sieve plates than the larger ones. This ultrastructural feature can be possibly correlated to a differential localization of the two classes of endothelial cells within the liver acinus.

Quantitative and qualitative histochemical investigation on NADP+-dependent dehydrogenases in the limiting plate and the residual parenchyma surrounding terminal hepatic venules

Activities of three NADP+-dependent enzymes (glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, isocitrate dehydrogenase) were demonstrated in the first layer of hepatocytes adjacent to terminal hepatic venules (perivenous limiting plate), and in the residual parenchyma of the perivenous zone of the acinus, in normally fed adult male Wistar rats, using a Lowry technique and a qualitative histochemical staining reaction. Enzyme activities of the glucose-6-phosphate dehydrogenase were significantly higher in the hepatocytes adjacent to terminal hepatic venules (ratio hepatocytes adjacent to terminal hepatic venules/residual parenchyma of the perivenous zone: 1.31). 6-Phosphogluconate dehydrogenase and isocitrate dehydrogenase were homogeneously distributed in the two areas measured (ratio: 1.04 and ratio: 1.0 respectively). With the qualitative histochemical staining reactions no differences were found.

Histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase

Histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase has found many applications in biomedical research. However, up to several years ago, the methods used often appeared to be unreliable because many artefacts occurred during processing and staining of tissue sections or cells. The development of histochemical methods preventing loss or redistribution of the enzyme by using either polyvinyl alcohol as a stabilizer or a semipermeable membrane interposed between tissue section and incubation medium, has lead to progress in the topochemical localization of glucose-6-phosphate dehydrogenase. Optimization of incubation conditions has further increased the precision of histochemical methods. Precise cytochemical methods have been developed either by the use of a polyacrylamide carrier in which individual cells have been incorporated before staining or by including polyvinyl alcohol in the incubation medium. In the present text, these methods for the histochemical and cytochemical localization of glucose-6-phosphate dehydrogenase for light microscopical and electron microscopical purposes are extensively discussed along with immunocytochemical techniques. Moreover, the validity of the staining methods is considered both for the localization of glucose-6-phosphate dehydrogenase activity in cells and tissues and for cytophotometric analysis. Finally, many applications of the methods are reviewed in the fields of functional heterogeneity of tissues, early diagnosis of carcinoma, effects of xenobiotics on cellular metabolism, diagnosis of inherited glucose-6-phosphate dehydrogenase deficiency, analysis of steroid-production in reproductive organs, and quality control of oocytes of mammals. It is concluded that the use of histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase is of highly significant value in the study of diseased tissues. In many cases, the first pathological change is an increase in glucose-6-phosphate dehydrogenase activity and detection of these early changes in a few cells by histochemical means only, enables prediction of other subsequent abnormal metabolic events. Analysis of glucose-6-phosphate dehydrogenase deficiency in erythrocytes has been improved as well by the development of cytochemical tools. Heterozygous deficiency can now be detected in a reliable way. Cell biological studies of development or maturation of various tissues or cells have profited from the use of histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Distribution and morphological characteristics of the pit cells in the liver of the rat

Pit cells, on which almost no further contributions have been presented since the first report by Wisse et al. (1976), are described in detail in the rat liver. These cells show several characteristic features: 1) "rod-cored vesicles", a new type of vesicular inclusion observed first in our study; 2) electron-dense granules, which we consider to arise from multivesicular bodies by the accumulation of dense material; and 3) well-developed pseudopodia. Although these features clearly differentiate pit cells from conventional lymphocytes, these two cell types display similarities (i) in a number of ultrastructural features, (ii) in the pattern of their intralobular distribution, and (iii) in their presence in the spleen and peripheral blood.

NADP-dependent dehydrogenases in rat liver parenchyma. III. The description of a liponeogenic area on the basis of histochemically demonstrated enzyme activities and the neutral fat content during fasting and refeeding

The activities of glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase(6PGDH), malic enzyme (ME) and isocitrate dehydrogenase (ICDh) were investigated with optimized histochemical methods (Rieder it al 1978), and the activity of 3-hydroxybutyrate dehydrogenase (3HBDH) and neutral fat content with conventional techniques in the liver of male rats under the following experimental dietary conditions: (A) Fasting for 0, 12 and 84h; (B) 84-h fasting followed by refeeding with a low-fat, high-carbohydrate diet for 6 h and for 2, 3, 5, 7, 11 and 14 nights; (C) refeeding with standard diet for 5 nights; (D) low-fat high-carbohydrate diet for 7 an 14 nights. The activities of G6PDH, 6PGDH and ME decreased slightly during fasting primarily in zone 1 and increased dramatically on refeeding with a low-fat, high-carbohydrate diet. This activity increase was confined mainly to zone 3 during the first 3 days and was accompanied by a deposition of neutral fats that began in zone 3 and progressed to zone 1. Neutral for accumulation was maximal after 3 nights, with a uniform accumulation of large droplets in all the hepatocytes; this was followed by a release that started in zone 3 and proceeded in a periportal direction. On the other hand, G6PDH, 6PGDH and ME attained their maximum activities after 5 amd 7 nights of low-fat diet, the activities being nearly homogeneously distributed over the liver acinus in a few cases. Subsequently the activities fill mainly in zone 1, causing the activity patterns and levels to approach those of the animals in group (D). In contrast to this, the activity of ICDH increased during fasting principally in zone 1, so that the otherwise steep activity gradient in favor of zone 3 lessened. Refeeding led at first to a fall of activity below the initial value, but later the normal distribution pattern was restored. The activity of 3HBDH showed a behavior similar to that of ICDH. The findings are discussed with reference to the functional heterogeneity of the liver parenchyma, and the existence of a liponeogenic area in zone 3 is proposed.

Quantitative aspects of the cytochemical demonstration of glucose-6-phosphate dehydrogenase with tetranitro BT studied in a model system of polyacrylamide films

The cytochemical determination of the activity of glucose-6-phosphate dehydrogenase (G6PDH) with tetranitro blue tetrazolium (TNBT) was studied with model films of polyacrylamide gel incorporating purified enzyme. This model system enabled a quantitative study to be made of different parameters involved with the cytochemical assay as it is applied to sections or smears. The enzyme activity of G6PDH incorporated in the model films was also assayed biochemically. Optimal conditions for retaining the maximum amount of enzymic activity are described. The behaviour of G6PDH towards enzyme inhibitors was found to be similar in model films and in solution. WIth TNBT, absorbance measurements at a single wavelength (535 nm) were used to estimate the enzyme activity quantitatively. When carried out under standardized conditions, both the cytochemical and biochemical assay showed a linear relation with the time of incubation and obeyed the Beer-Lambert law. The correlation between biochemical and cytochemical data was very high, which enabled cytochemical data to be converted into absolute units of enzyme activity. The data obtained in this way closely resembled the data of enzyme activity calculated from the absorbance of formazan produced inside polyacrylamide model films and afterwards extracted into a suitable solvent.

High activity of glucose-6-phosphate dehydrogenase in Kupffer cells isolated from rat liver

Sinusoidal cells in the rat liver react intensively for G6DPH activity after appropriate incubation (Rieder et al. 1978). After isolation and purification of the sinusoidal Kupffer and endothelial cells, it was demonstrated that Kupffer cells exhibit a 5-8 times higher G6PDH activity on a per cell basis by comparison with endothelial cells, while the specific G6PDH activity was 3-4 times higher in Kupffer cells. The Kupffer cells can be divided into two groups which differ significantly in G6PDH activity calculated on a per cell basis. In histochemical studies, G6PDH can be used as a marker for Kupffer cell identification.

NADP-dependent dehydrogenases in rat liver parenchyma. II. Comparison of qualitative and quantitative G6PDH distribution patterns with particular reference to sex differences

Qualitative histochemical G6PDH distribution patterns obtained in the liver acinus of adult male and female rats with an improved method (Rieder et al., 1978) served as a basis for the isolation by microdissection of tissue samples of defined zonal affiliation. G6PDH activity was assayed quantitatively in tissue samples of zones 1 and 3 by a microfluorometric method, using the oil well technique and enzymatic cycling (Burch et al., 1963; Lowry and Passonneau, 1972). With the use of a correlation system further evidence could be presented for the validity of the recently described qualitative distribution patterns. From a total of 50 analyzed tissue samples the following G6PDH activities were calculated: 4.25 +/- 1.56 U/g dry weight in zone 1 and 2.08 +/- 0.46 U/g dry weight in zone 3 of male and 7.21 +/- 1.03 U/g dry weight in zone 1 and 11.10 +/- 2.56 U/g dry weight in zone 3 of female rats. These data were corrected for interference from the G6PDH activity of the Kupffer cells within zone 1 samples (approximately 80 U/g dry weight), so that the actual relative values for the parenchymal activity could be estimated for the first time: 2 U/g dry weight in zones 1 and 3 of male animals, 5 U/g dry weight in zone 1 and 11 U/g dry weight in zone 3 of female animals. In female livers G6PDH activity in zone 1 is therefore 2.5 times higher, and in zone 3 5 times higher than in the male. These zonal as well as sex-differences are clearly indicative of a heterogeneous functional organization of the liver acinus in terms of capacity for NADPH production, mainly in connection with reductive reactions in fatty acid synthesis.