New Micromethods for Studying Sublobular Structure and Function in the Isolated, Perfused Rat Liver

Lemasters, John J.; Ji, Sungchul; Thurman, Ronald G.

doi:10.1007/978-1-4684-5041-5_7

Cited by 14 publications

(3 citation statements)

References 21 publications

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“…. each describes the same design but from a different perspective" (Lemasters et al, 1986); and "are not conflicting, but rather represent different interpretations of certain aspects of hepatic structure and function" (Jones, 1990).…”

Section: Current Trendsmentioning

confidence: 99%

Liver units in three dimensions: I. organization of argyrophilic connective tissue skeleton in porcine Liver with particular reference to the “compound hepatic lobule”

Ekataksin

Wake

1991

Am. J. Anat.

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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.

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Section: Current Trendsmentioning

confidence: 99%

Liver units in three dimensions: I. organization of argyrophilic connective tissue skeleton in porcine Liver with particular reference to the “compound hepatic lobule”

Ekataksin

Wake

1991

Am. J. Anat.

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“…Changes in oxygen concentration were measured when the flow was stopped, allowing rates of oxy gen uptake to be calculated [64]. Interesting ly, rates of oxygen uptake were 2-to 3-fold higher in periportal than in perivenous re gions of the liver lobule [64][65][66][67][68][69], and it was shown that regional rates of oxygen uptake are determined by the local oxygen concen tration by mechanisms involving calcium the whole organ by the difference between influent and effluent concentration.…”

Section: Fluxes In Vitro Studied With Noninvasive Techniques Local Ramentioning

confidence: 99%

Hepatocyte Heterogeneity in the Metabolism of Carbohydrates

Jungermann

Thurman²

1992

Enzyme

Self Cite

109

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Periportal and perivenous hepatocytes possess different amounts and activities of the rate-generating enzymes of carbohydrate and oxidative energy metabolism and thus different metabolic capacities. This is the basis of the model of metabolic zonation, according to which periportal cells catalyze predominantly the oxidative catabolism of fatty and amino acids as well as glucose release and glycogen formation via gluconeogenesis, and perivenous cells carry out preferentially glucose uptake for glycogen synthesis and glycolysis coupled to liponeogenesis. The input of humoral and nervous signals into the periportal and perivenous zones is different; gradients of oxygen, substrates and products, hormones and mediators and nerve densities exist which are important not only for the short-term regulation of carbohydrate metabolism but also for the long-term regulation of zonal gene expression. The specialization of periportal and perivenous hepatocytes in carbohydrate metabolism has been well characterized. In vivo evidence is provided by the complex metabolic situation termed the ‘glucose paradox’ and by zonal flux differences calculated on the basis of the distribution of enzymes and metabolites. In vitro evidence is given by the different flux rates determined with classical invasive techniques, e.g. in periportal-like and perivenouslike hepatocytes in cell culture, in periportal- and perivenous-enriched hepatocyte populations and in perfused livers during orthograde and retrograde flow, as well as with noninvasive techniques using miniature oxygen electrodes, e.g. in livers perfused in either direction. Differences of opinion in the interpretation of studies with invasive and noninvasive techniques by the authors are discussed. The declining gradient in oxygen concentrations, the decreasing glucagon/insulin ratio and the different innervation could be important factors in the zonal expression of the genes of carbohydrate-metabolizing enzymes. While it is clear that the hepatocytes sense the glucagon/insulin gradients via the respective hormone receptors, it is not known how they sense different oxygen tensions; the O(2) sensor may be an oxygen-binding heme protein. The zonal separation of glucose release and uptake appears to be important for the liver to operate as a ‘glucostat’. Thus, zonation of carbohydrate metabolism develops gradually during the first weeks of life, in part before and in part with weaning, when (in rat and mouse) the fat- and protein-rich but carbohydrate-poor nutrition via milk is replaced by carbohydrate-rich food. Similarly, zonation of carbohydrate metabolism adapts to longer lasting alterations in the need of a ‘glucostat’, such as starvation, diabetes, portocaval anastomoses or partial hepatectomy.

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“…A miniature oxygen electrode was constructed by inserting a 50 pm diameter platinum wire into a glass capillary that was pulled under heat. The electrode tip was coated with a n oxygen-permeable polymer, and the finished electrode was connected to a standard oxygen electrode polarization and amplification circuit described previously (18). To measure local rates of oxygen uptake, electrodes were placed on periportal and pericentral regions, and flow was stopped by clamping the outflow and stopping the inflow simultaneously (19).…”

Section: Rates Of Oxygen Uptake In Periportal and Pericentralmentioning

confidence: 99%

Carbohydrate and oxygen metabolism during hepatocellular proliferation: A study in perfused livers from mirex-treated rats

Yarbrough

1991

Hepatology

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Liver regeneration after partial hepatectomy is accompanied by altered hepatic intermediary metabolism. Because the organochlorine compound mirex also causes liver cell growth, the purpose of this study was to investigate hepatic carbohydrate and oxygen metabolism in perfused livers from mirex-treated rats and to localize cell proliferation in this model. Pretreatment with mirex (100 mg/kg, intragastrically) increased liver/body weight ratios and DNA synthesis in livers of fed rats, effects that were markedly diminished in livers of fasted rats. This finding shows that liver growth caused by mirex, as is the case after partial hepatectomy, is hindered when animals are deprived of food. Furthermore, perfused livers from mirex-treated rats had depleted glycogen stores but significantly elevated oxygen uptake compared with livers from control rats. Increases in oxygen uptake and hepatocellular proliferation were observed mostly in periportal regions of the liver lobule. In regenerating livers, most DNA synthesis was reported to also occur in these regions of the liver lobule. Taken together, these data show that liver cell growth caused by mirex is accompanied by changes in hepatic intermediary metabolism and sublobular proliferation similar to those observed after partial hepatectomy.

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New Micromethods for Studying Sublobular Structure and Function in the Isolated, Perfused Rat Liver

Cited by 14 publications

References 21 publications

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 in three dimensions: I. organization of argyrophilic connective tissue skeleton in porcine Liver with particular reference to the “compound hepatic lobule”

Hepatocyte Heterogeneity in the Metabolism of Carbohydrates

Carbohydrate and oxygen metabolism during hepatocellular proliferation: A study in perfused livers from mirex-treated rats

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