Regionality of glucose-6-phosphate hydrolysis in the liver lobule of the rat: metabolic heterogeneity of "portal" and "septal" sinusoids

Antidiabetic effect of konjac glucomannan via insulin signaling pathway regulation in high-fat diet and streptozotocin-induced diabetic rats

Type 2 diabetes mellitus is a chronic metabolic disorder that tends to disarray various metabolic pathways. Dietary-mediated T2DM prevention garners much attention in recent decades. Hence, this study was intended to elucidate the antidiabetic properties of Konjac glucomannan (KGM) in diabetic rats. Our experimental design includes five groups, with six rats in each group. Group 1 feeding standard diet pallet alone served as control rats; group 2 was KGM control rats administered intragastrically with KGM (120 mg/kg b.w.). Group 3 was developed as diabetic rats with a high-fat diet and an intraperitoneal injection of Streptozotocin-40 mg/kg b.w. Group 4 were diabetic rats treated with KGM (80 mg/kg b.w.), and group 5 were diabetic rats received rosiglitazone treatment (4 mg/kg b.w.). The results showed that STZ-induced diabetic rats significantly elevate liver marker enzymes and gluconeogenesis enzymes. Diminished glycolytic enzymes, liver glycogen, insulin signaling genes, and proteins were also seen in diabetic rats. Treatment with KGM augmented glycolytic enzymes and liver glycogen. On the other hand, KGM diminished gluconeogenesis, liver marker enzymes, upregulated gene, and protein expression of the insulin pathway. The current results suggest dietary KGM can offer a better health benefit in the treatment of T2DM.

Early developmental influences on hepatic organogenesis

The liver is the largest of the body's organs, with the greatest number of functions, playing a central role in coordinating metabolic homeostasis, nutrient processing and detoxification. The fetal liver forms during early gestation in response to a sequential array of distinct biological events, regulated by intrinsically programmed mechanisms and extracellular signals which instruct hepatic cells to either proliferate, differentiate or undergo apoptosis. A vast number of genes are involved in the initiation and control of liver development, many of which are sensitive to nutritional and hormonal regulation in utero. Moreover, liver mass is influenced by the gestational environment. Therefore, during periods of hepatic cell proliferation and differentiation, the developing fetal liver is sensitive to damage from both internal and external sources including teratogens, infection and nutritional deficiencies. For example, fetuses exposed to decreased materno-fetal nutrition during late gestation have a reduced liver mass, and/or perturbed liver function, which includes increased plasma LDL cholesterol and fibrinogen concentrations. These occur in conjunction with other risk factors present in the early stages of cardiovascular disease i.e. decreased glucose tolerance and insulin insensitivity in later life. Taken together, these findings suggest that liver mass, and later function, are essentially set in utero during fetal development-a process that is ultimately regulated by the intrauterine environment.

Assessment and histological analysis of the IPRL technique for sequential in situ liver biopsy

BACKGROUND

The isolated perfused rat liver (IPRL) is a technique used in a wide range of liver studies. Typically livers are assessed at treatment end point. Techniques have been described to biopsy liver in the live rat and post-hepatectomy.

RESULTS

This paper describes a technique for obtaining two full and one partial lobe biopsies from the liver in situ during an IPRL experiment. Our approach of retaining the liver in situ assists in minimising liver capsule damage, and consequent leakage of perfusate, maintains the normal anatomical position of the liver during perfusion and helps to keep the liver warm and moist. Histological results from sequential lobe biopsies in control perfusions show that cytoplasmic vacuolation of hepatocytes is a sign of liver deterioration, and when it occurs it commences as a diffuse pattern which tends to develop a circumscribed, centrilobular pattern as perfusion progresses.

CONCLUSIONS

Liver lobe biopsies obtained using this method can be used to study temporal effects of drug treatments and are suitable for light and electron microscopy, and biochemical analyses.

Revelation of simple and complex liver acini after portal transplantation of pancreatic islets or thyroid follicles in rats

The microarchitecture of the liver is still not completely understood although various concepts of structural liver organization have been proposed. Among them, Rappaport's liver acinus stands out as one of the most accepted models. The correctness of this model, however, has also been doubted, and its applicability is hampered by the fact that the outlines of the liver acinus are disguised and nobody was ever able to give visual evidence by "unmasking" a simple liver acinus from the surrounding liver tissue. After intraportal transplantation of pancreatic islets or thyroid follicles into diabetic or thyroidectomized rats, respectively, the transplants engraft in small portal tracts and morphologically alter the downstream liver tissue due to excessive hormone secretion. Using a combined approach of perfusion fixation, stereomicroscopy, and light microscopy, we demonstrate in this study that these foci of altered liver tissue represent simple and complex liver acini, exactly as described by Rappaport. We present stereomicroscopical and histological examples of all important cut levels of altered simple and complex liver acini, including their topographical relation to the supplying and draining vessels and to the "central vein" liver lobule. Moreover, by computer-aided reconstruction of serial semi-thin sections, we were able to present the first 3-dimensional images of simple and complex liver acini.

CONCLUSION

Our results prove the correctness of Rappaport's acinus model and confirm the simple liver acinus as the principal microcirculatory unit of the liver.

The modular microarchitecture of human liver

The morphological homogeneity of the liver parenchyma has represented a major obstacle in finding an acceptable definition of the structural/functional units of the liver. Concepts such as the "lobule," the "portal unit" and the "acinus" remain debatable. This study investigates the modular microarchitecture on the basis of the lobular concept. Using alkaline phosphatase activity as a histochemical marker, modules could be recognized clearly. In autopsy specimens of human liver, modules were traced through sequential cryosections, and a "secondary" module having a height of 1.9 mm, a surface of 14.7 mm(2), and a volume of 5.1 mm(3) was reconstructed three-dimensionally. It was subdivided into 14 "primary" modules by portal tracts and vascular septa and by a common draining central venular tree. Primary modules were polyhedral, with seven to nine facets, having heights from 0.3 to 0.9 mm, surface areas from 1.7 to 5.0 mm(2), and volumes from 0.1 to 0.9 mm(3). Such variation in shape and size is considered an important part of the modular organization of the human liver. In conclusion, the findings on the three-dimensionality and microcirculation of liver modules support and extend the lobular concept and, at the same time, make apparent the shortcomings of the concepts of acinar and portal units. The results of this study should permit a better interpretation of histological sections of normal and pathological liver and provide a basis for understanding the metabolic heterogeneity of liver cells and their functional integration into parenchymal units.

Validation of confocal laser scanning microscopy for detecting intracellular calcium heterogeneity in liver slices

To investigate changes in the intracellular Ca(2+) ([Ca(2+)]i) in liver lobules under aerobic and hypoxic conditions, we measured [Ca(2+)]i in liver slices using a confocal laser scanning microscope (CLSM). The liver lobule is divided into 3 equal parts between the central vein and portal area, Zones 1, 2, and 3 from the portal side. [Ca(2+)]i in each zone of cultured rat liver lobules was measured by CLSM and a fluorescent Ca(2+) indicator (Rhod 2 AM). After the culture solution was changed to an Na(+)-free solution under aerobic conditions, the percentage of cells showing an increase in [Ca(2+)]i was 66.0+/-9.7% in Zone 1, 70.0+/-10.5% in Zone 2, and 94.0+/-9.7% in Zone 3. The percentage was significantly higher in Zone 3 than in Zones 1 and 2 (P< .01). Under hypoxic conditions, the percentage of cells showing an increase in [Ca(2+)]i was 6.0+/-9.7% in Zone 1, 8.0+/-10.3% in Zone 2, and 10.0+/-10.5% in Zone 3. There were no differences among the 3 zones. In all zones, the percentage was higher under aerobic conditions than under hypoxic conditions (P< .01). These results indicated that the increase in [Ca(2+)]i in liver lobules was heterogeneous. Measurement of [Ca(2+)]i in liver slices by CLSM was considered useful for studying heterogeneity between liver lobules, as well as between liver cells.

Three-dimensional observations of spatial arrangement of hepatic zonation and vein system in mice and house musk shrews

The three-dimensional (3D) relationship among the hepatic domains and the efferent central and afferent portal veins was investigated by macroscopy, microscopy, and computer-aided 3D reconstruction methods. To clearly distinguish the pericentral domain from the periportal, we used CCl(4)-treated mice and diabetic house musk shrews, which show typical pericentral necrosis and deposition of fat, respectively. The 3D findings obtained were verified against normal control animals using advantages of our unique observations by light and fluorescent microscopy, which made it possible to differentiate the two domains well. The pericentral domains in the mice and shrews appeared three-dimensionally as continuous branched columns, and the periportal domains exist in a sponge-like network that fills the parenchymal space among the columnar pericentral domains. The efferent central veins were concentrically surrounded by the pericentral domain, and segments of the central veins flowed into large sublobular and lobar veins. The walls of these large veins faced the pericentral domain at the confluence with the central veins; the remaining portions of the walls faced the periportal domain. The afferent portal veins were placed at the two-dimensional center of the network of the periportal domain and gave off smaller portal branches radially at the intersections of the network. Three types of liver lobules-classic, portal, and acinar-have been discussed repeatedly at the (2D) level. At the 3D level, it is reasonable to consider that the liver parenchyma consists of the two continuous domains corresponding to the distribution of the vessels that we found.

Lobular distribution pattern of lactate dehydrogenase and 6-phosphogluconate dehydrogenase activity in rat liver

Lactate dehydrogenase (LDH) and 6-phosphogluconate dehydrogenase (6-PGDH) activities were measured in lobular areas expanding between 3 portal tracts and an efferent central vein in the livers of male Wistar rats, using a Lowry technique. The maximum of LDH activity was found in a nearly uniform broad area in the lobular periphery. From that area values decreased along periportal/septal-->perivenous gradients, but only slightly within that area along the periportal-->septal axis of the vascular septum. Maximum values of 6-PGDH activity were present in an intermediate area close to the central vein demonstrating a rather inhomogeneous distribution pattern without a clear definition of zonal limits. Our data on the distribution pattern of LDH are in agreement with the concept of the metabolic lobulus and are supported by a recent evaluation of the vascular architecture in rat liver. The lobular distribution pattern of 6-PGDH cannot be interpreted without doubt in accordance with that concept.

Three-dimensional reconstruction of parenchymal units in the liver of the rat

To investigate the parenchymal units in the liver of the rat three-dimensionally, 15 micrometer cryosections were used for the demonstration of glucose-6-phosphatase (G6Pase) activity to visualize the borders of the individual units. Together with the supplying and draining vessels, they were traced through a sequence of 146 sections and reconstructed. A cone-shaped secondary unit with a height of 2.1 mm and a volume of 3.3 mm3 was reconstructed. It was "covered" by a continuous vascular surface, consisting of portal tracts and vascular septa, connecting the portal venular branches. The secondary unit was subdivided by portal tracts and vascular septa, and by branches of a draining central venular tree into 14 primary units. Most of them were tri- to heptahedral in shape. The height varied between 330 and 840 micrometer, and the volume varied between 0.094 and 0.621 mm3. The branches of the portal venular tree, with diameters from 28 +/- 5 micrometer to 61 +/- 14 micrometer, were oriented preferentially along the vertical axis of the units. Most of the primary units were drained by single branches of the central venular tree, located in the center and oriented along the vertical axis of the units. Vessel diameters ranged from 62 +/- 14 micrometer to 216 +/- 9 micrometer. The average length of the sinusoids was 355 +/- 3 micrometer. From the results of this reconstruction study, it was concluded that the concept of the liver acinus cannot be applied to the liver of the rat.

Zonal and regional differences identified from precision mapping of vitamin A-storing lipid droplets of the hepatic stellate cells in pig liver: a novel concept of addressing the intralobular area of heterogeneity

Knowledge of hepatic heterogeneity has been strikingly increased, while an accurate means for addressing intralobular positions is still lacking. We examined pig liver preparations of the gold impregnation method for vitamin A-storing lipid droplets in hepatic stellate cells. Droplet morphometry was performed under oil immersion, and the calculated volumes plotted on computerized maps. The heterogeneous results were assessed with five concentric zones and five radial regions; the latter were determined based on midseptum visualized by portal injection. Zonation and regionation thus subdivided lobules into 5-zone/5-region (5Z/5R) compartmentalization. Distribution of values exhibited a distinct zonal gradient, heightened at peripheral zones 1 and 2, decreased over intermediate zone 3 toward centrilobular zones 4 and 5; peak was always found at zone 2. Within a single zone, variations were obvious, forming a regional gradient. Values were significantly higher at periportal than midseptal regions. Digitized mapping showed that low values filled up centrilobular zones, whereas high values concentrated in periportal regions. Along the periphery, inlet venules were quantified, revealing an occurrence rate of 60% at periportal, and 5% at midseptal regions, closely compatible with the regional gradient of vitamin A-storing capacity. The interweaving between zonal and regional gradients results in a vitamin A-low territory, a compound area composed of centrilobular zones plus extensions into midseptal regions. Because the results could account for physiological and pathological events, we regard the 5Z/5R compartmentalization a model worth routine adoption for a precise description of any morphofunctionally demonstrable heterogeneity of the liver lobules.

The portal lobule in rat liver fibrosis: a re-evaluation of the liver unit

We re-evaluated three schemes of liver organization: the classic lobule, the portal lobule, and Rappaport's liver acinus. The lobular angioarchitecture of normal rat liver and the three-dimensional structure of pseudolubules found in rat livers with fibrosis induced by swine serum were compared with the classic lobule of the pig. Normal and fibrotic rat livers and pig livers were perfused, injected with either India ink or 0.75% OsO4 through the portal and/or hepatic vein, and immersionfixed. Whole lobes and hand-cut thick sections were made transparent with a solution of benzyl benzoate and methyl salicylate. The angioarchitecture of normal rat liver differs from pig liver. In the former, terminal portal branches and central veins interdigitate, and in the latter, numerous terminal portal branches that arise from interlobular portal veins establish a vascular basket surrounding one central vein and forming classic lobule. The structure of liver acinus is never found in the pig liver. The terminal portal branch, together with the terminal hepatic artery and bile duct, are present inside each pseudolobule of fibrotic rat livers. Blood from the terminal portal branch flows through inlet venules into radiating sinusoids, and, at the periphery converges into newly formed septal and angular outlet venules; these venules terminate in fibrotic central veins located at each corner. Pseudolobules are not rugby ball-like as Rappaport's liver acini are but are polyhedron in shape. The rat pseudolobules are comparable with the portal lobule; its structure and microcirculation are the reverse of the pig classic lobule. Rat pseudolobules are different from liver acini, as shown by the following: 1) their three-dimensional shape is different; and 2) they have a reverse relationship to classic lobules while acini are defined to subdivide classic lobules. In normal and fibrotic rat livers, the liver unit is the portal lobule with a terminal portal branch as the axial branch and central veins at the periphery. The co-existence of liver acini and classic lobules is doubtful.

In situ measurement of glutamate concentrations in the periportal, intermediate, and pericentral zones of rat liver

We developed a quantitative histochemical assay for measurement of local glutamate concentrations in cryostat sections of rat liver. Deamination of glutamate by glutamate dehydrogenase (GDH) was coupled to the production of formazan and formazan precipitation was used for colorimetric visualization. The method was tested and validated with gelatin model sections with known glutamate concentrations. Calibration graphs showed linear relationships with high correlation coefficients (> 96%) between glutamate concentrations or section thickness and absorbance values. The method was reproducible, with a constant percentage of 60 +/- 5% of glutamate being converted in gelatin model sections containing glutamate concentrations of 2 mM and higher. Glutamate concentrations were estimated in periportal, intermediate, and pericentral zones of liver lobules that contain low, intermediate, and high GDH activity, respectively. In fed adult male rat livers, periportal zones contained the highest concentrations of glutamate (approximately 14 mM) and intermediate and pericentral zones approximately 13 and 9 mM, respectively. On starvation, glutamate concentrations increased only in the small rim of pericentral cells that express glutamine synthetase, to approximately 15 mM. In livers of fetal and newborn rats, glutamate was homogeneously distributed, with a concentration of approximately 5 mM. In suckling rat liver, distribution of glutamate was still homogeneous but the concentration was increased to approximately 8 mM. These glutamate distribution patterns were in agreement with those detected immunohistochemically.

Quantitative analysis of glycogen content in hepatocytes of portal and central lobule zones of normal human liver and in patients with chronic hepatitis of different etiology

Glycogen content was determined in hepatocytes of different lobule zones of the normal human liver (23 patients without any liver pathology) and the liver of patients with chronic viral B hepatitis (30 patients) and chronic alcohol hepatitis (28 patients). All the patients were males and aged between 17-50 years. Quantitative analysis of the glycogen content in hepatocytes of portal and central lobule zones was carried out in sections of the human liver (material of functional biopsies) stained with PAS-reaction. The measurements were carried out using an image analyser 'Magiscan' which allows combined cytophotometric analysis of a substance in cells and determination of the cell localization in tissue. The results showed significant differences of the glycogen content in different lobule zones in the normal liver and in the liver in chronic viral and alcohol hepatitis. Ratios of glycogen content in hepatocytes of the portal and the central zones of liver lobule were 1.128 +/- 0.004 and 1.061 +/- 0.003 in normal human liver, and liver of patients with chronic viral hepatitis respectively, i.e. the glycogen content in hepatocytes of the portal lobule zone was much higher than in the central lobule zone in the normal liver and in the liver of patients with chronic viral B hepatitis. The ratio in patients with chronic alcohol hepatitis was less than 1.0 (0.930 +/- 0.003), i.e. a significantly higher glycogen content was found in hepatocytes of the central liver lobule zone. Possible mechanisms of this phenomenon are discussed. Thus, the pattern of the glycogen content in hepatocytes of different lobule zones can be used as an indicator of etiology of chronic hepatitis.

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.

Predominant periportal expression of the phosphoenolpyruvate carboxykinase gene in liver of fed and fasted mice, hamsters and rats studied by in situ hybridization

Zonal expression of phosphoenolpyruvate carboxykinase (PCK) mRNA in mouse, hamster and rat liver was studied by in situ hybridization with a radiolabelled rat antisense RNA probe. The abundance of PCK mRNA was determined by Northern blot analysis of total RNA with a digoxigenin-labelled probe. Livers were taken from animals that were sacrificed during the normal day/night cycle and after 29 h fasting. In situ hybridization revealed a heterogeneous distribution pattern of PCK mRNA in the liver of all three species throughout the whole day/night cycle. At the end of the dark period, i.e. at the end of feeding, with rats and mice but at a point of continuous feeding with hamsters, low amounts of PCK mRNA were restricted mainly to the periportal area. At the end of the light period, i.e. at the end of fasting with rats and mice but at a point of continuous feeding with hamsters, PCK mRNA levels were increased to a maximum and extended from the periportal to the intermediate zone. In mouse liver prolonged fasting caused a significant increase in PCK mRNA abundance with a nearly homogeneous distribution within the parenchyma. In hamster and rat liver, however, PCK mRNA levels slightly declined or remained constant, respectively, and the predominant localization of PCK mRNA in the periportal and intermediate zone was preserved. The present data suggest that the heterogeneous zonal activation of the PCK gene was essentially very similar in mouse, hamster and rat liver.

Histological evaluation of the zonation of colloidal gold uptake by the rat liver

The distribution and endocytotic function of Kupffer cells in the rat liver were studied after administration of fibrinogen stabilized colloidal gold suspensions either by injection directly into the circulatory system of anaesthetized rats or by application to the isolated perfused liver. After exposure to gold particles the livers were perfused with fixative and studied using several microscopic techniques. Gold was predominantly endocytosed by a highly active population of Kupffer cells surrounding the portal spaces resulting in distinct dark patterns around the terminal portal veins. In cross-sections of lobules the pattern appeared as incomplete networks composed of dark triangular areas with distinct borderlines towards light areas concentric with the terminal hepatic veins (central veins). The light areas contained few and relatively inactive small Kupffer cells. A wide variation of conditions gave essentially the same uptake pattern compatible with the concept of microcirculatory zones concentric with the terminal hepatic veins (Lamers et al., 1989; Quistorff and Rømert, 1989), but contradicting the traditional view of microcirculatory zones advanced by Rappaport et al. (1954). Since the same pattern developed during conditions of anoxia, it seems that oxygen is not the stimulus for the developmental distribution of Kupffer cells with high endocytotic activity. In vivo and perfusion experiments gave identical patterns, but a higher endocytotic activity of endothelial cells was found in perfused isolated livers.

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.

Liver units in three dimensions: I. Organization of argyrophilic connective tissue skeleton in porcine liver with particular reference to the "compound hepatic lobule"

Liver units were investigated in pig livers by means of histologic serial tracing, physical model building, and computer-aided three-dimensional imaging. Observations of the argyrophilic connective tissue skeleton were based mainly on the celloidin-embedded serial sections treated with silver impregnation. The parenchymal mass that clothed the initial segments of hepatic venous radicles was demarcated by fibrous septa which formed isolable units with two basic patterns: the simple hepatic lobule (SHL) and the compound hepatic lobule (CHL). Both lobule types presented regular limiting structures circumscribing each unit. Three-dimensional studies revealed that 25% of the lobules in a section belonged to the SHL type and 75% to the CHL type, the latter being predominant among the surface lobules. When considered in only two dimensions, however, the SHL-like lobules constituted the majority. Polygonal analysis disclosed that the pentagonal lobule was the most typical, instead of the "hexagonal" or "classic" lobule. The CHLs represented a multiaxial unit containing a system of venous tributaries in accordance with intralobular septation, whereas the SHLs were found with one axial vessel having a dendritic tendency at the incipient end; some SHLs were drained eccentrically by separate vessels into a sublobular vein. It was observed that, in dividing CHLs, whereas particular sinosoids were transformed into portal twigs, other sinusoids were changed into central venous tributaries. Fibrous deposition occurred along the septal-line sinusoids, bringing into view the septum-initiating plane. Fibroconnective tissue was supplied from the portal area and central (sublobular) adventitia, where portal triad structures and adventitial arterioles, respectively, were included. The findings of the present study facilitate the understanding of several characters of the lobules that have been reported previously, or occasionally postulated, such as the portal-central bridging tendency, the intralobular arterioles or ductules, the translobular artery or portal vein, the "portal-portal" or "portal-central" anastomoses, and the apposition of pericentral zone close to periportal zone. Based on differences in argyrophilia of sinusoidal reticulum, in proportion of lobule types, and in vasculature, the anatomic heterogeneity of liver unit was demonstrable in zonality, regionality, and locality.

Estimating anatomical-functional position coordinates in liver tissue

Hepatocyte enzyme activity was demonstrated by examining adult C57BL/6 mouse liver cryostat sections under a succinate dehydrogenase (SDH) histochemical reaction, and quantified by microspectrophotometry and microdensitometry. The hepatocyte SDH activity gradient along the path between the portal veins (PV) and efferent terminal hepatic venules (THV) was analyzed by measuring the concentration of the chromophore precipitated in 10 consecutive hepatic parenchymal domains located along imaginary lines drawn across the entire PV-to-THV distance. The profiles of intensity or of normalized relative optical density obtained on a high number of lines were correlated with distance values along the PV-to-THV pathway, enabling us to establish a general mathematical function relating SDH activity (chromophore concentration) to position values on a scale of 0 to 10 corresponding to the theoretical PV-to-THV distance. The equation can be used to interpolate the SDH activity surrounding any intrahepatic object located between the PV and the THV, thus making it possible to calculate the object's anatomical-functional position coordinates in the liver acinus. To demonstrate how this method is used, we have calibrated the intrahepatic position of hemopoietic foci induced in the liver tissue of adult mice treated with phenylhydrazine (PHZ), and show that these foci are located on coordinate 3.31 (maximum range 1.25-4.86) of the sinusoidal domain-that is, on the borderline between Rappaport's acinar zones 1 and 2.

Adaptative changes of metabolic zonation during the development of cirrhosis in growing rats

To evaluate changes in liver metabolic zonation during development of juvenile cirrhosis, zonal activities of succinate dehydrogenase, glutamate dehydrogenase, glucose-6-phosphatase, and nicotinamide adenine dinucleotide phosphate (NADPH) dehydrogenase were measured by quantitative cytochemistry in the liver of developing rats intoxicated with carbon tetrachloride and phenobarbitone. During treatment, activities were most decreased in perivenular zones and subsequently at the periphery of the cirrhotic nodules for succinate dehydrogenase and glucose-6-phosphatase, whereas glutamate dehydrogenase and NADPH dehydrogenase were less affected. In the periportal zones, enzyme activities decreased less. After stopping intoxication, the rats remained cirrhotic, but enzyme activities returned to control perivenular levels at the periphery of the cirrhotic nodule and to control periportal levels at its center. It is concluded that a metabolic zonation persists in carbontetrachloride/phenobarbitone-induced juvenile cirrhosis and that enzyme activities can recover despite persisting cirrhosis. In this model, afferent vessels seem to be located at the center of the cirrhotic nodules, and efferent vessels, at their periphery. A different metabolic zonation may exist in other human and animal liver cirrhosis that could be related to the site of initial liver damage.

The application of quantitative cytochemistry to study the acinar distribution of enzymatic activities in human liver biopsy sections

The zonal distribution of enzyme activities was measured by quantitative cytochemistry in cryosections of liver from three normal children and five infants with idiopathic hepatitis of infancy. Optimal conditions for cytochemical reactions were first validated in rat liver and subsequently used in human livers to quantify zonal activities of acid phosphatase (AP), succinate dehydrogenase (SDH), glutamate dehydrogenase (GDH), glucose-6-phosphatase (G6P) and NADPH-dehydrogenase (ND). In normal rat and human livers, activities were greater for SDH and G6P in periportal and for GDH and ND in perivenular hepatocytes, while AP was evenly distributed along the sinusoids. In five infants with idiopathic hepatitis of infancy (IHI), a similar trend of distribution was observed for the two mitochondrial (SDH and GDH) and the two microsomal (G6P and ND) enzymes, although the distribution gradient was less pronounced than, in normal livers. AP showed a mildly greater periportal than perivenular activity. This preliminary study shows that a similar metabolic zonation exists for these enzymes in human livers as is observed in rats.