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At least 19 recordsLinked to original sources
PubMed2026

Human umbilical cord-derived mesenchymal stem cell exosomes ameliorate hepatocyte ferroptosis and sepsis-associated liver injury by restoring iron homeostasis in hepatocytes.

Mesenchymal stem cells-derived exosomes (MSCs-Exo) constitute critical mediators of intercellular communication between stem cells and other cell types. Among these, exosomes derived from human umbilical cord mesenchymal stem cells (HUMSCs-Exo) have attracted considerable attention owing to their potent immunomodulatory capacity, low surface antigenicity, and favorable biosafety profile. Accumulating evidence indicates that HUMSCs-Exo can attenuate ferroptosis in target tissues across a spectrum of pathological conditions, including inflammatory bowel disease and viral cardiomyopathy, thereby mitigating tissue injury, improving organ function, and prolonging host survival. Nevertheless, the regulatory effects of HUMSCs-Exo on sepsis-associated liver injury (SALI) and hepatocellular ferroptosis, as well as the underlying molecular mechanisms, remain largely undefined. In this study, we identified pronounced differential gene expressions between control and septic mice hepatocytes, particularly within pathways related to iron metabolism, lipid metabolism, and ferroptosis. Building on these findings, we systematically characterized the dynamic progression of hepatocyte ferroptosis in septic mice through integrated in vivo and in vitro experiments, demonstrating a strong positive correlation between ferroptotic activity and the severity of liver injury. Using wild-type male C57BL/6J mice and the murine normal hepatocyte cell line NCTC1469, we further demonstrated that HUMSCs-Exo markedly upregulate the expression of FPN, xCT, GPX4, and FTH1 while concomitantly downregulating ACSL4 and TFRC. These molecular alterations reduced intracellular lipid peroxidation and labile iron accumulation, thereby robustly attenuating sepsis-induced hepatocyte ferroptosis and conferring significant hepatoprotective effects. Finally, these findings were validated in the immortalized human normal hepatocyte cell line THLE-2, in which HUMSCs-Exo similarly suppressed lipopolysaccharide-induced ferroptosis and cellular injury by modulating intracellular lipid peroxide and free iron levels. Collectively, our results demonstrate that HUMSCs-Exo exert potent inhibitory effects on sepsis-induced hepatocyte ferroptosis and confer protection against liver injury, primarily through the restoration of intracellular iron homeostasis and the suppression of lipid peroxidation. This study provides a novel therapeutic strategy for the treatment of SALI and ferroptosis.

Ferroptosis↗
PubMed1975

[Influence of hypothyreodism on the quantitative Karyo- and cytoarchitecture of rat hepatocytes. (A morphometrical and cytophotometrical study on rat hepatocytes 3 weeks after thyreoidectomy) (author's transl)].

INTRODUCTION: Thyroid hormoned influence the quantitative cytoarchitecture of hepatocytes by stimulating the membrane synthesis of mitochondria and ergastoplasm. The cellular and nuclear changes produced by thyroidectomy were analysed cytophotometrically and morphometrically. MATERIAL AND METHODS: 21 days after thyroidectomy the liver tissues of 10 male Wistar rats were examined. 5 sham-operated animals served as controls. All rats received Altromin-R-standard diet. The cytophotometric analysis is based on the method described by Sandritter. The morphometric study was carried out following Weibel's methods. RESULTS AND DISCUSSION: As a consequence of the changed cellular metabolism, smaller hepatocytes and nuclei (but larger nucleoli) are found in the hypothyroid rats. As compared with controls, hepatocytes hardly show tetraploid nuclei, which is due to inhibited polyploidisation. The mitochondrial content has become considerably smaller in the hypothyroid hepatocytes. The cristal membranes, the mitochondrial and peroxysomal volume per hepatocyte show a similar reaction pattern, which is considered to be a sign of reduced cellular metabolism. The volume loss of the ergastoplasm confirms this assumption.

Animals↗
PubMed1975

Functional polarity of the rat hepatocyte surface membrane. Isolation and characterization of plasma-membrane subfractions from the blood-sinusoidal, bile-Canalicular and contiguous surfaces of the hepatocyte.

1. Six rat liver plasma-membrane subfractions of different density and morphological, enzymic and chemical properties were prepared from homogenates by a combination of differential, rate-zonal and density-gradient centrifugation. They consisted of three vesicular 'light' subfractions of density 1.12-1.13 and three 'heavy' subfractions of density 1.16-1.18 containing membrane strips and intercellular junctions. 2. All six subfractions contained a basal adenylate cyclase activity. One of the 'light' subfractions that showed the highest glucagon-stimulated adenylate cyclase activity was identified as deriving form the blood-sinusoidal face of the hepatocyte. This subfraction, unlike the others, was contaminated by Golgi components, as indicated by its morphological properties and the presence of galactosyl- and sialyl-transferase activities. 3. All the six subfractions showed high activities of the following plasma-membrane marker enzymes: 5'-nucleotidase, alkaline phosphodiesterase (nucleotide pyrophosphatase), alkaline phosphatase, leucine naphthylamidase and Mg2+-activated adenosine triphosphatase. A 'light' subfraction that showed the highest specific activities of all the above marker enzymes, but lacked a glucagon-stimulated adenylate cyclase activity, was identified as deriving from the bile-canalicular face of the hepatocyte. 4. The 'heavy' subfractions, which showed generally the lowest activities of the above plasma-membrane enzyme markers, and were characterized by the presence of desmosomes and gap junctions, were taken to originate from the contiguous faces of the hepatocyte. 5. The protein composition of the six subfractions was generally similar, as shown by polyacrylamide-gel electrophoresis. Differences in the amounts of various protein and glycoprotein bands among the subfractions correlated with their morphology, enzymic composition and sialic acid content. 6. Hormonal and histochemical evidence supporting the identification of a bile-canalicular subfraction, a blood-sinusoidal subfraction and contiguous-face subfractions is discussed.

Adenosine Triphosphatases↗
PubMed1977

[In vitro synthesis of alpha-fetoprotein by individual hepatocytes and microcolonies of human hepatocytes].

Alpha-fetoprotein (AFP) produced by individual hepatocytes and hepatocyte microcolonies was detected with microelectrophoresis-precipitation in polyacrylamide gel. Hepatic cells of 6--13-week-old human embryos were cultivated in vitro for 2 to 5 days. 23 of 28 individual cells, and 89 of 91 microcolonies, built up of 2--35 cells, were demonstrated to produce AFP within the range of 70--800 pg per cell.

Cells, Cultured↗
PubMed1976

Studies with mature rat hepatocytes in monolayer culture. I. Propagation of isolated hepatocytes, morphological and biochemical in culture.

Differentiated cells have been established in monolayer culture from adult rat liver and their ultrastructural and biochemical features characterized after 20-30 generations. Hepatocytes were isolated by enzyme perfusion of the liver followed by treatment with papain, which allowed cultures to be established more readily and to be cloned at an early stage. Ultrastructural studies indicated that the cells were derived largely from hepatic parenchymal cells. The cells showed structural modifications during primary culture but were stable thereafter. The cultured cells retained some differentiated functions unique to liver cells, including the synthesis of ornithine form arginine and the secretion of serum proteins, albumin, chi- and beta-globulins.

Animals↗
PubMed1976

Separation of intact rat hepatocytes and rat liver nuclei into ploidy classes by velocity sedimentation at unit gravity.

A system is described which permits the separation of isolated hepatocytes and isolated rat liver nuclei belonging to different ploidy classes by velocity sedimentation at unit gravity. The problem of obtaining single cells suspensions is discussed and preparations were obtained that contained 96% single hepatocytes. By improving the sedimentation method, it took 2.5 h to separate rat liver nuclei on sucrose gradients into diploid and tetraploid ploidy classes. Recoveries were generally over 95%. The diploid band was 99% pure. DNA and protein content of the ploidy classes were measured. After partial hepatectomy and [3H]thymidine injection it was found that the label moved largely into the tetraploid compartment. Isolated hepatocytes were fractionated in 1 h on Ficoll gradients. Erythrocytes were separated from small nucleated cells and the population of hepatocytes was clearly separated from these two cell populations. Diploid hepatocytes were 80% and tetraploid hepatocytes were 99% pure. Viability was about 80% after fractionation. The gene dosage of NADPH cytochrome c reductase, succinate dehydrogenase and lactate dehydrogenase was estimated in diploid and tetraploid hepatocytes. Gene dosage was equal in diploid and tetraploid hepatocytes for succinate dehydrogenase and NADPH cytochrome c reductase. It is suggested, after correcting for non-viable tetraploid hepatocytes, that the gene dosage of lactate dehydrogenase was significantly lower in diploid than in tetraploid hepatocytes.

Animals↗
PubMed1975

Comparison of 125-I-insulin binding and degradation to isolated rat hepatocytes and liver membranes.

UNLABELLED: We have compared the ability of rat liver plasma membranes and isolated hepatocytes to bind and degrade insulin. Isolated cells were prepared in two different ways: by mechanical separation of cells and by collagenase digestion of extracellular matric. In all studies the binding and degradative characteristics of both types of hepatocyte preparations were identical. Furthermore, with one exception, the binding characteristics of membranes and cells were also quite similar. The only exception concerned the amount of insulin bound by hepatocytes as compared to liver membranes. Thus, at concentrations of cells (1.2 times 10(6) cells per milliliter) and membranes (150 mug. protein per milliliter) that gave equal binding at insulin concentrations less than 100 ng./ml., the amount of insulin specifically bound at insulin concentrations greater than 100 ng./ml. was greater with use of hepatocytes. Additional studies indicated that, in contrast to membranes, at the higher insulin concentration only 75 per cent of the previously bound insulin could be recovered from hepatocytes. Thus, a nondissociable component exists; which probably represents intracellular radioactivity and appears to account for the higher specific insulin binding by cells at higher insulin concentrations. When insulin degradation was studied at the above hepatocyte and plasma membrane concentrations, cells degraded 30 per cent more insulin than did membranes. Kinetic analysis of these data revealed that the Km for insulin degradation (5 times 10(-7) M at 37 degrees) was the same for both systems wereas the Vmax was greater with use of hepatocytes. IN CONCLUSION: (1) Preparation of hepatocytes by collagenase digestion does not appear to alter insulin binding or degradation; (2) studies of liver membranes and isolated hepatocytes obtained from normal rats should yield similar information about insulin-receptor interaction as long as insulin concentrations less than 100 ng./ml. are used; (3) at very high insulin concentrations, some of the radioactivity appears to enter the cells; (4) the kinetics of insulin degradation by hepatocytes and liver membranes are similar; and (5) insulin degradation appears to be primarily a membrane phenomenon.

Animals↗
PubMed1979

Primary cultures of hepatocytes on human fibroblasts.

Parenchymal hepatocytes isolated from adult rats were cultured on three types of collagen-containing substrata: collagen-coated plates, collagen membranes and confluent diploid human fibroblasts. Hepatocytes on the latter two substrata maintained characteristic morphology for at least 10 days in culture, whereas degenerative changes (cell death and formation of multinucleated hepatocytes) and growth of nonparenchymal elements were seen after 5 days in cultures on collagen-coated plates. Parallel findings were seen on basal and induced levels of cytochrome P-450 and NADPH-cytochrome C reductase. The basal levels of cytochrome P-450 were not measurable after day 3 in hepatocytes cultured on collagen-coated plates, whereas measurable levels were maintained in the hepatocytes cultured on the other two substrata. Addition of phenobarbital or methylcholanthrene at day 5 in culture caused an increase in cytochromes P-450 and P-448, respectively, only in hepatocytes cultured on collagen membranes and confluent fibroblasts. Analogous results were seen for the enzyme NADPH-cytochrome C reductase. The similarities in performance between hepatocytes on collagen membranes and on human fibroblasts show that a continuous collagen-containing substratum is important for optimal performance of hepatocytes in primary culture. The possible importance of cultures of hepatocytes on human fibroblasts for carcinogenesis studies is discussed.

Animals↗
PubMed1975

Isolation and subfractionation on ficoll gradients of adult rat hepatocytes. Size, morphology, and biochemical characteristics of cell fractions.

The recirculating perfusion of adult rat liver with a Ca-++-free Hanks' solution produces a release of the adhesiveness of cells and a cleaving of the desmosomes. The addition of collagenase and hyaluronidase to the perfusion medium leads to complete dissociation of the liver tissue into a mixture of isolated cells and cell cords in which the hepatocytes remain connected with specific junctional differentiations, namely the gap and tight junctions. Individual cells are released by submitting the suspension of cell trabeculae to a gentle rolling. The gap junctions are ruptured at least in one of the two adjacent cells and remain generally attached to the other cell taking with them a small portion of cytoplasm. This technique of isolation of hepatocytes yields about 60-65% of the parenchymal cells contained in a liver; endothelial cells and other cells of the connective tissue are not recovered. The ultrastructural preservation of the isolated hepatocytes is excellent and the glucose-6-phosphatase activity, confined to the endoplasmic reticulum, appears unaltered in most cells. Protein, DNA and RNA recovery in the preparations of isolated hepatocytes is satisfactory, amounting to 70% of that found in liver homogenate; glycogen, the most labile component examined, is partly lost or degraded during the manipulations. Cell diameters measured by different methods confirm the preservation of the original volume of the in situ hepatocytes and the presence of more than one type of parenchymal cell. By submitting this heterogeneous cell population to an isopycnic density gradient centrifugation, two types of hepatocytes can be distinguished: the light hepatocytes, with a mean diameter of 20.5 mum and a mean density of 1.10, are characterized by an extended smooth-walled endoplasmic reticulum entrapping dispersed alpha-glycogen particles; the heavy hepatocytes, with a mean diameter of 19.0 mum and a mean density of 1.14, present a relatively reduced compartment of smooth endoplasmic reticulum, but large accumulations of glycogen. It is suggested that the cell fraction of low density is enriched in centrolobular cells and the high density fraction in perilobular hepatocytes.

Animals↗
PubMed1978

Induction of cytochrome P-450 in a selective subpopulation of hepatocytes.

The objective of this study was to determine whether the inductive effect of phenobarbital (PB) on liver cytochrome P-450 was the result of the action of this drug on all or some hepatocytes. For this purpose, a light (cell band I) and a heavy (cell band II) subpopulation of hepatocytes were separated from rat liver in a continuous density gradient. To determine the location of these hepatocytes in tissue, [14C]bromobenzene, which binds covalently to centrilobular hepatocytes, was administered. The specific activity (14C dpm/mg protein) was greater in cells of band I than in cells of band II, suggesting a predominant contribution of centrilobular hepatocytes to the lighter cell band. Microsomes were separated from each cell subpopulation after 3 days of PB administration and cytochrome P-450 was measured. Although a fivefold increment in cytochrome P-450 content of light hepatocytes was noted, the content of heavy hepatocytes was similar to that of the respective subpopulation in controls. Concomitantly, PB administered for 3 days induced the smooth endoplasmic reticulum of centrilobular hepatocytes only, as revealed by electron microscopy of whole tissue. These results indicated that PB induces cytochrome P-450 in a selective subpopulation of hepatocytes, most likely located near the terminal hepatic venule.

Animals↗
PubMed1978

Effect of glucagon and insulin on the growth of neonatal rat hepatocytes in primary tissue culture.

Commercial (bovine-porcine) glucagon added in a single dose between 10(-12) and 10(-7) M to neonatal rat hepatocytes in primary cultures with subsequent incubation for 20-24 h, stimulated their entry into the DNA synthesis phase as revealed by [3H]thymidine-labeling and radioautography; about 14 h of incubation was required before an effect was observed. Commercial (bovine) insulin at doses between 10(-11) and 10(-7) M apparently stimulated the entry of hepatocytes into S phase. However, insulin's effect, which needed 20 h for induction, was due to the release of a wave of synchronized hepatocytes from an earlier produced block near the G1/S boundary of their growth-division cycle. Equimolar mixtures of glucagon with insulin from 10(-15)-10(-7) M increased the fraction of hepatocytes synthesizing DNA first at 4-8 h, and then at 20-24 h. Effective doses of glucagon, insulin, and glucagon plus insulin also increased the entry of hepatocytes into mitosis, as found after a 4-h incubation with colchicine (0.1 mM). Withholding inactivated fetal bovine serum from the growth medium for 24 h did not change the mitotic activity either of the untreated or of the glucagon- and glucagon plus insulin-stimulated hepatocytes, but it increased the proliferogenic effect of bovine insulin. Highly purified crystalline (porcine) glucagon, insulin, and glucagon plus insulin also stimulated the growth of hepatocytes in the presence or absence of serum. Finally, equimolar (10(-14) M) mixtures of glucagon with (Bu)2cGMP and of insulin with (Bu)2cAMP increased the hepatocytic replication as efficiently as did glucagon plus insulin at the same dose. The present results show that glucagon and insulin are synergistic, intracycle regulators of the growth of neonatal rat hepatocytes. They also suggest that cyclic necleotides may mediate at least partly the hepatotropic effects of the pancreatic hormones.

Animals↗
PubMed1975

Stimulation of adenylate cyclase from isolated hepatocytes and Kupffer cells.

Hepatocytes and Kupffer cells were separated from rat liver after prelabeling the Kupffer cells with colloidal iron and perfusion of the liver with digestive enzymes. The activity of several enzymes from Kupffer cells and hepatocytes was compared to validate this method of cell separation. The ratios of hepatocyte to Kupffer cell specific activities of glucose-6-phosphatase, 5'-nucleotidase, adenylate cyclase, and acid phosphatase were 20, 0.39, 0.18, and 0.078, respectively. Adenylate cyclases from hepatocytes and Kupffer cells were stimulated by fluoride ion, GTP, and catecholamines. Hepatocyte adenylate cyclase was also stimulated by glucagon, secretin, vasoactive intestinal polypeptide, and by prostaglandin E1, whereas, the Kupffer cell enzyme was completely insensitive to these hormones. The stimulation of hepatocyte adenylate cyclase by combinations of glucagon plus secretin, or glucagon plus vasoactive intestinal polypeptide, were equivalent to the sum of the individual stimulations. This suggests that the hepatocyte has specific receptors for glucagon and for vasoactive intestinal polypeptide and secretin. Prostaglandin E1 stimulation of hepatocyte adenylate cyclase was not additive to the stimulation caused by polypeptide hormones or catecholamines, nor did prostaglandin E1 decrease stimulation caused by these hormones. Although prostaglandin-sensitive adenylate cyclase was recovered with hepatocytes, 40 to 50% of the total liver prostaglandin-sensitive activity was recovered in a fraction of cell debris mixed with small cells which did not phagocytize colloidal iron.

Adenylyl Cyclases↗
PubMed2026

Single-nucleus profiling reveals hepatocyte identity and immune features associated with corticosteroid response in severe alcohol-related hepatitis.

BACKGROUND & AIMS: Severe alcohol-related hepatitis (sAH) is associated with high short-term mortality. However, 30-40% of patients fail to respond to corticosteroids, the only proven pharmacological treatment. The pathophysiological mechanisms underlying sAH and the marked heterogeneity in treatment response remain incompletely understood. We aimed to define cellular changes associated with corticosteroid response in sAH and to identify baseline markers predictive of treatment outcome. METHODS: Single-nucleus RNA sequencing was performed on liver biopsies from patients with biopsy-proven sAH (n = 17), including paired baseline and day 8 biopsies in a subset of patients (n = 8). Patients were classified as corticosteroid responders (sAH-R; Lille score <0.45) or non-responders (sAH-NR; Lille score &#x2265;0.45). Liver biopsies from patients with acute decompensation of alcohol-related cirrhosis (AD; n = 5) and healthy controls (n = 4) were included for comparison. Findings were validated using immunohistochemistry and spatial proteomics in a large multicenter validation cohort (n = 172). RESULTS: At baseline, sAH-R exhibited a significantly higher proportion of liver-infiltrating S100A8+ monocytes compared to sAH-NR, a difference that persisted at day 8. sAH livers showed a marked reduction in mature hepatocytes and an expansion of stressed and intermediate hepatocyte populations, indicating progressive loss of mature hepatocyte identity. This loss was more pronounced in sAH-NR, who also exhibited fewer cycling hepatocytes at day 8, consistent with impaired regenerative capacity. Expression of SULT2A1, a marker of mature hepatocyte identity, was significantly reduced in sAH-NR at baseline. Finally, liver biopsies with &#x2265;50% SULT2A1-positive hepatocytes at baseline were strongly predictive of corticosteroid response. CONCLUSIONS: This study delineates distinct immune and hepatocyte changes associated with corticosteroid response in sAH. Baseline SULT2A1 expression may facilitate stratified treatment approaches in sAH. IMPACT AND IMPLICATIONS: Severe alcohol-related hepatitis (sAH) represents one of the most devastating manifestations of alcohol-related disorders. sAH is characterized by acute hepatic inflammation and high short-term mortality. Clinical management remains challenging, as corticosteroids - the only pharmacological therapy currently applied - are ineffective in a substantial proportion of patients and are associated with significant adverse effects. These limitations highlight the need for a more detailed understanding of sAH pathophysiology and for approaches that enable improved patient stratification and therapeutic decision-making. In this study, we identify distinct pre-treatment differences between corticosteroid responders and non-responders at the level of both hepatocytes and myeloid cells, providing new insight into the cellular mechanisms underlying treatment heterogeneity in sAH. Furthermore, leveraging these findings, we developed a histology-based SULT2A1 scoring system using a commercially available antibody, which predicts corticosteroid response at baseline and may support stratified treatment approaches in clinical practice.

Humans↗
PubMed2025

Targeting hepatocyte-specific SLC2A8 blocks hepatic steatosis and dissociates TCA cycle flux inhibition from glutamine anaplerosis.

BACKGROUND: Excess TCA cycle and glutamine anaplerosis are hallmarks of metabolic dysfunction-associated steatotic liver disease and steatohepatitis. Blocking glutamine metabolism attenuates metabolic dysfunction-associated steatohepatitis. However, inhibiting TCA cycle flux by blocking plasma membrane carbohydrate transport is limited by the ubiquitous tissue distribution, function, and homology among the SLC2A family of facilitative carbohydrate transporters, and the potential for carbohydrate blockade to invoke or exacerbate glutamine anaplerosis. Here, we quantify alterations in hepatocyte carbon flux, define the broader metabolic consequences of hepatocyte-specific GLUT8/SLC2A8 inhibition, and delineate the antisteatotic efficacy of a novel small-molecule GLUT8-selective inhibitor. METHODS: We generated mice with floxed SLC2A8 alleles and expressed hepatocyte-specific Cre by breeding these mice with albumin-Cre transgenic mice, or by administering AAV8 encoding hepatocyte-specific iCre. We performed stable-isotope glucose, fructose, and glutamine metabolic labeling in isolated GLUT8WT and GLUT8LKO hepatocytes and performed metabolic phenotyping in lean and diet-induced obese GLUT8WT and GLUT8LKO mice. Finally, we performed high-throughput screening to identify a GLUT8-selective inhibitor, which we characterized using in vitro models of triglyceride accumulation. RESULTS: Hepatocyte-specific SLC2A8 deletion reduced diet-induced hepatic and peripheral fat accumulation and increased thermogenesis during ZT12-24 (eg, the dark phase). It also disrupted TCA cycle flux without inducing compensatory glutamine utilization. High-throughput screening identified a small-molecule, GLUT8-selective inhibitor, P20, which blocked hepatocyte TG accumulation and inflammation in in vitro steatotic and inflammatory models. CONCLUSIONS: Deleting the hepatocyte carbohydrate transporter GLUT8 suppresses TCA cycle flux without inducing compensatory glutamine anaplerosis. The net effect of this is liver protection against multiple forms of dietary insult. Given that selective pharmacological GLUT8 inhibition is feasible, GLUT8 may be a viable target to abate metabolic dysfunction-associated steatohepatitis and other complications of obesity.

Animals↗
PubMed1978

Calcium metabolism in rat hepatocytes.

1. The total calcium concentration in rat hepatocytes was 7.9 microgram-atoms/g dry wt.; 77% of this was mitochondrial. Approx. 20% of cell calcium exchanged with 45Ca within 2 min. Thereafter incorporation proceeded at a low rate to reach 28% of total calcium after 60 min. Incorporation into mitochondria showed a similar time course and accounted for 20% of mitochondrial total calcium after 60 min. 2. The alpha-adrenergic agonists phenylephrine and adrenaline + propranolol stimulated incorporation of 45Ca into hepatocytes. Phenylephrine was shown to increase total calcium in hepatocytes. Phenylephrine inhibited efflux fo 45Ca from hepatocytes perifused with calcium-free medium. 3. Glucagon, dibutryl cyclic AMP and beta-adrenergic agonists adrenaline and 3-isobutyl-1-methyl-xanthine stimulated calcium efflux from hepatocytes perifused with calcium-free medium. The effect of glucagon was blocked by insulin. Insulin itself had no effect on calcium efflux and it did not affect the response to dibutyryl cyclic AMP. 4. Incorporation of 45Ca into mitochondria in hepatocytes was stimulated by phenylephrine and inhibited by glucagon and by carbonyl cyanide p-trifluoromethoxyphenylhydrazone. The effect of glucagon was blocked by insulin. 5. Ionophore A23187 stimulated hepatocyte uptake of 45Ca, uptake of 45Ca into mitochondria in hepatocytes and efflux of 45Ca into a calcium-free medium.

Animals↗