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The uptake of dodecanedioic acid (C12); a dicarboxylic acid with 12 carbon atoms, was studied in the isolated perfused rat liver. Fifty mumol of C12 were injected as a bolus into the perfusing liver solution. The concentration of C12 in perfusate samples taken over 2 h from the beginning of the experiments were analyzed by high performance liquid chromatography. An in vitro experimental session was performed to determine the binding curve of C12 to defatted bovine serum albumin. These data were then used to compute the perfusate C12 free fraction. The number of binding sites on the albumin molecule was equal to 4.29 +/- 0.21 (S.E.), while the affinity constant was 6.33 +/- 0.87 x 10(3). M-1. Experimental values of perfusate C12 concentration versus time were individually plotted and fitted to a monoexponential decay for each liver perfused. The predicted C12 concentration at time zero averaged 0.354 +/- 0.0375 mumol/ml. Prom this value the apparent volume of distribution of C12 was obtained and corresponded to 153.02 +/- 14.56 ml. The disappearance rate constant from the perfusate was 0.0278 +/- 0.0030 min-1. The C12 half life was 26.6 +/- 2.3 min. The mean hepatic clearance from the perfusate was 4.08 +/- 0.38 ml/min. In conclusion, C12 is quickly taken up by the liver so that in about 100 min it was completely cleared from the perfusate.

Biliary cholesterol represents one of the two major excretory pathways for sterol elimination from the body and plays a central role in cholesterol gallstone formation. Biliary cholesterol originates from a precursor pool of preformed and newly synthesized free cholesterol. Although it has been suggested that newly synthesized and preformed biliary cholesterol are secreted by independent pathways, the specific cellular and molecular mechanisms are unknown. We used male Wistar rats to study the time-course of the appearance of newly synthesized cholesterol, phosphatidylcholine and protein into bile. The specific role of sterol carrier protein-2 (SCP-2) in the transport of newly synthesized biliary cholesterol was evaluated by an in vivo antisense oligonucleotide approach. In contrast to [14C]phosphatidylcholine and [35S]proteins, the time-course of [14C]cholesterol appearance into bile was rapid, and microtubule- and Golgi-independent. In vivo SCP-2 antisense treatment reduced and delayed the appearance of biliary [14C]cholesterol. Furthermore, hepatic SCP-2 expression increased more than 3-fold over control values in rats that had been treated with diosgenin to increase biliary secretion of newly synthesized cholesterol. These results suggest that SCP-2 is necessary for the rapid transport of newly synthesized cholesterol into bile and that hepatocytes can induce SCP-2 expression according to the rate of biliary secretion of newly synthesized cholesterol.

Background/aims: Bile salts (BS) are cytotoxic agents, but cell damage is not observed in the hepatobiliary system. We hypothesized that biliary lipid vesicles (unilamellae and multilamellae) could have a protective role against BS-induced cytotoxicity., Methods: Biliary lipid lamellar secretion was induced by feeding rats with 0.5% diosgenin. Cytoprotection was assessed in bile duct-obstructed rats and by incubating human erythrocytes with sodium taurocholate., Results: Biliary cholesterol concentration increased > 300% in diosgenin-fed rats; electron microscopic examination showed a great abundance of lipid lamellar vesicles in bile and within the canaliculi. After bile duct obstruction, serum hepatic enzyme activities were significantly lower in diosgenin-fed rats. Histologically severe and confluent hepatocellular necrosis was only observed in control rats. Biliary lamellar lipid material significantly reduced the BS-induced hemolytic effect in vitro in a concentration-dependent manner. This protective effect correlated to a progressive decrease in the intermicellar BS concentration. Phosphatidylcholine or cholesterol, alone or as lamellar structures, also showed cytoprotective effect in vitro but always less than native biliary lamellae., Conclusions: These results support the concept that native biliary cholesterol phospholipid lamellae represent an important cytoprotective factor for hepatocytes and biliary epithelial cells against BS-induced damage.

In vitro hepatic synthesis of lipids starting from (1-14C)acetate was investigated for 14 days in rats with biliary obstruction by ligation of the common bile duct using radio-thin-layer chromatography (radio-TLC). This study was correlated with a quantitative assay of the various hepatic lipids using TLC correlated with photodensitometry. Hepatic total lipid synthesis increased progressively with time. With concern to the single fractions, the major modifications were verified on the 3rd day with a decreased incorporation of the labelled acetate into the triglycerides. On the other hand, using photodensitometry, they demonstrated a percentage increase. These variations can be justified by the presence of a feedback mechanism. The syntheses of cholesterol and the other fractions were maximum during this period. Histologic examination revealed, especially on the 3rd day, a neoformation of biliary ductules and on the 14th day, a regression of these histological changes.

In vitro hepatic synthesis of lipids starting from 1-(14)C-acetate was studied in rats made diabetic by subcutaneous alloxan administration (175 mg/kg b.w.). A second group of diabetic rats was treated with lente insulin. In the alloxan-treated rats, a decrese was observed in hepatic incorporation of 1-(14)C-acetate into phospholipids, triglycerides and esterified cholesterol; there was an increased incorporation into nonesterified fatty acids (NEFA) and free cholesterol. Insulin administration restored lipid synthesis values to normal. On histologic examination, an intranuclear glycogenesis was observed in the hepatocytes of the alloxan-treated rats, along with severe hepatic necrosis; the latter however, only in rats sacrified on the 3rd day. Hepatic steatosis with small, medium and large droplets was present in the insulin-treated rats; signs of cellular degeneration were less evident.

The aim of the present study is to determine the "in vitro" rate of 1-14C-acetate incorporation into lipids in human liver slices from patients with various types of hyperlipoproteinemia. Hepatic tissue from type IIa hyperlipemic patients incorporated labelled acetate into free cholesterol at a higher rate than normolipidemic patients. In type IIb patients the incorporation was increased into hepatic free cholesterol, triglycerides and FFA. The liver of pre-beta hyperlipoproteinemic subjects incorporated 1-14C-acetate into triglycerides to a greater extent than hepatic tissue from controls. Triglyceride synthesis was highly elevated in type IV hyperlipoproteinemic patients with diabetes. In all cases, there was no significant correlation between increased hepatic triglyceride synthesis (dpm/mg of extracted lipids) and insulin response (microunits/ml) to oral glucose ingestion (75 g). The present data indicates that in the presence of disturbances in lipid and carbohydrate metabolism one observes an alteration of lipid synthesis in the liver. The in vitro incorporation of 1-14C-acetate into hepatic cholesterol and/or triglyceride in patients with primary hyperlipoproteinemia is increased. Thus the elevated serum cholesterol and triglyceride levels of these patients could be explained on the basis of an increased lipoprotein synthesis in the liver.

The plasma clearance rate of high density lipoprotein is reduced in the hypothyroid rat. Because the liver is an important site of HDL-cholesterol catabolism, the present study was undertaken to investigate whether thyroid hormone deficiency affects binding of HDL to liver cells. Male Wistar rats were made hypothyroid by feeding propylthiouracil (0.1% w/w). Liver cells were isolated by in situ perfusion of the liver with a buffered collagenase solution. 125I-labelled rat HDL binding to isolated liver cells was carried out at low temperature on ice. For both control and hypothyroid rat liver cells, 125I-HDL binding was significantly inhibited by excess unlabelled rat HDL and also by human HDL3 and human LDL but was unaffected by the addition of 10 mM EDTA. From Scatchard analysis of dose-response studies, hypothyroid cells displayed a lower HDL binding capacity (P less than 0.01) and a higher binding affinity (P less than 0.025) compared to control cells. These results suggest that thyroid hormone affects the expression of the HDL binding site in liver cells which may contribute to the reduced HDL clearance in the hypothyroid animal.

The lipid composition of hepatic and gallbladder bile was examined in 20 patients with cholesterol gallstones and in 20 control subjects. Lipid fractions other than bile salts, phospholipids and cholesterol were found to be present, i.e., sterol esters, non-identified fractions and, above all, free fatty acids. The latter probably originated from biliary phospholipids via activity of phospholipases, present in the gallbladder wall. No significant difference in amount and pattern of free fatty acids and phospholipids was found in hepatic bile between patients with gallstones and controls. On the contrary, we observed relevant differences in the lipid composition of gallbladder bile. In this way, we consider that the bile becomes lithogenic inside the gallbladder as a consequence of release of free fatty acids, particularly if these are constituted by saturated chains. In fact, these can compete with cholesterol in the solubilization in biliary micelles. On the other hand, free fatty acids can be directly toxic for the gallbladder wall and produce a cholecystitis.

In a patient with Behcet's syndrome the finding of five times the normal level of serum transaminase accompanied by weakness may be correlated to the syndrome itself. We performed needle biopsy of the liver in our patient which showed piecemeal necrosis and portal lympho-monocytic infiltration extending into the lobule. It is interesting that HLA B5 and B27 antigens were present. Simultaneous occurrence of chronic active hepatitis and Behcet's syndrome may imply the same autoimmune pathogenesis, as we suggest in this work.

Chenodeoxycholic and ursodeoxycholic acids reduce significantly the hepatic synthesis of lipids in rats. The present study has been carried out using (1-14C)acetate and evaluating its incorporation into different lipidic fractions of the liver by thin-layer radiochromatography. Ursodeoxycholic acid proved to be more active than chenodeoxycholic acid: in addition to a significant decrease of the hepatic incorporation of the acetate into cholesterol and triglycerides an increase of the hepatic incorporation of the acetate into phospholipids has been observed. The exogenous administration of bile acids diminishes the hepatic synthesis of cholesterol and therefore its biliary excretion; it enriches the bile acid and phospholipid pool in the liver and bile. By this way the action of bile acids establishes in the liver a condition which induces such an increase of availability of mixed micelles in the bile as to make it unsaturated in cholesterol.

The effect of insulin deficiency on lipid synthesis in the liver of normal rats, diabetic rats by alloxan and pancreatectomized rats was studied in vitro using (1-14C) acetate as lipid precursor. Insulin deficiency induces an increased incorporation of (1-14C) acetate into triglycerides in rat liver. This is particularly evident in pancreatectomized rats with respect to alloxan diabetic rats. It is concluded that in experimental diabetes an atherogenous metabolic pattern is elaborated by the liver.

In psoriatic patients with hyperlipidemia we studied the hepatic lipid synthesis from (1-(14)C)-acetate in human liver biopsy specimens in vitro by a thin-layer radio-chromatography. In psoriatics type IV (according to Fredrickson) a significant increase in (1-(14)C)-acetate hepatic incorporation especially into phospholipids (25%) and triglycerides (52%) was observed; in type IIb increased lipogenesis was phospholipids (24.5%), free cholesterol (44.4%) and triglycerides (29%). Abnormal lipid metabolism often coexists with glucose intolerance in psoriasis; no correlation between hyperinsulinemia and augmented (1-(14)C)-acetate incorporation into hepatic triglycerides was found.