The galactose elimination capacity as a quantitative measure of liver function in acute carbon tetrachloride intoxication of rats

Noninvasive evaluation of liver disease severity

In assessing the severity of chronic liver disease, one measures either the fibrotic structure of the liver or liver function. This article reviews the methods for evaluating the severity of liver disease noninvasively by estimating function or structure.

Acute carbon tetrachloride feeding selectively damages large, but not small, cholangiocytes from normal rat liver

The aim of this study was to develop a model of selective duct damage restricted to hormone-responsive segments corresponding to the ducts damaged in primary biliary cirrhosis (PBC). Carbon tetrachloride (CCl4) was fed by gavage to rats, and 2, 7, 14, and 28 days later, small and large cholangiocytes were isolated. Apoptosis was determined in situ by morphology and in purified cholangiocytes by assessment of nuclear fragmentation by 4, 6-diamidino-2-phenylindole (DAPI) staining. Cholangiocyte proliferation was evaluated in situ by morphometry of liver sections stained for cytokeratin-19 (CK-19) and by proliferating cellular nuclear antigen (PCNA) staining in liver sections and in purified cholangiocytes by PCNA gene expression. Ductal secretion was assessed by measurement of secretin receptor (SR) gene expression and secretin-induced cyclic adenosine 3',5'-monophosphate (cAMP) synthesis and secretin-induced choleresis. Two days after CCl4 administration, there was an increased number of small ducts, but a reduction of large ducts. Apoptosis, observed only in large ducts, was associated with decreased DNA synthesis and ductal secretion. Conversely, small cholangiocytes expressed de novo the SR gene and secretin-stimulated cAMP synthesis 2 days after CCl4 treatment. Proliferation of large cholangiocytes was delayed until 7 days, which was associated with a transient increase in ductal secretion in vivo. CCl4 effects on cholangiocytes were reversed by day 28. CCl4 treatment causes a decrease in large duct mass as a result of a higher rate of apoptosis and absence of initial proliferation in large cholangiocytes. These processes were concomitant with a decrease of ductal secretion in large cholangiocytes. Small cholangiocytes appear resistant to CCl4-induced apoptosis, and proliferate and transiently compensate for loss of proliferative and secretory activity of large cholangiocytes.

Application of hepatic tolerance tests to the functional reserve assessment in rat models of fatty liver

The present study was designed to define whether maximal removal rate of indocyanine green (ICG Rmax), plasma cyclic 3',5'-adenosine monophosphate (cAMP) response to exogenous glucagon (peak to basal ratio of cAMP level: P/B cAMP) and plasma half-life of galactose (t1/2 galactose) can measure the hepatic functional reserve of fatty liver prepared in rats fed choline-deficient (9 weeks), 2% cholesterol (2 weeks) or 0.25% DL-ethionine (2 weeks) diet. Although changes in cholesterol and phospholipid values in serum during feeding periods differed among the models, histopathologic examinations in the liver of almost all animals revealed intermediate to severe fatty liver with or without fibrosis at each termination. ICG Rmax and P/B cAMP were significantly decreased in rats fed choline-deficient or DL-ethionine diet, implying reductions in hepatic functional mass and disturbances in hepatic cAMP production. Meanwhile, t1/2 galactose showed no change in any of the models, suggesting that glucose metabolisms in the models used may be preserved. These findings demonstrate that ICG Rmax and P/B cAMP can apply to measurement of hepatic surviving reserve of fatty liver with fibrosis.

Functional status of the liver during chronic renal failure: an experimental study in the rabbit

Quantitative and qualitative measures of liver function were investigated in rabbits with chronic renal failure (CRF) induced 3 months earlier by surgical reduction of renal mass, and compared with a sham-operated control group. In the CRF group the galactose elimination capacity (GEC) was significantly decreased by 25%, but when related to liver weight the difference was not statistically significant. The clearance of antipyrine was unaffected. The serum activities of alanine aminotransferase, lactate dehydrogenase and alkaline phosphatase were similar in the two groups. The prothrombin index was increased by 20%, and the serum albumin concentration decreased by 9%. By light microscopy no significant morphological changes were found in the livers of the CRF rabbits. The results do not indicate significant changes of the hepatic functional status during moderate chronic renal insufficiency.

Liver function during chronic renal failure in rabbits

In rabbits with chronic renal insufficiency the prothrombin index was increased by 25% and the alanine aminotransferase activity decreased by 20%; the results of other routine tests of hepatic function were not affected. The galactose elimination capacity was decreased by 12%, whereas the body clearance of antipyrine was unchanged. No change in hepatocytic structure was found.

Galactose elimination kinetics in perfused rat liver after two thirds hepatectomy

Galactose elimination kinetics was studied in isolated perfused livers (single pass) from rats subjected to two thirds partial hepatectomy 6 h earlier or immediately before investigation. No difference was found between the two groups in the maximum galactose elimination rate or in the half saturation galactose concentration. This is in contrast with in vivo observation of restored galactose elimination capacity 6 h after two thirds hepatectomy. The discrepancy indicates that extrahepatic factors may be of importance for the metabolic regulation in the liver during regeneration.

Kinetics of galactose uptake by perfused rat livers: applicability of a family of models

Mathematical models for general substrate uptake mechanisms in the liver have been used to describe the kinetics of galactose removal. In this study sets of galactose uptake rates to galactose concentration relations obtained by perfusion of ten livers of 200 g rats were examined. The rate of galactose uptake (v) was related to the galactose concentration in the sinusoids (calculated as the logarithmic mean of in- and outlet concentration, ĉ). In all experiments a saturation pattern emerged, but the resulting 1/v versus 1/ĉ plots were all markedly convex, discarding simple Michaelis-Menten kinetics. Data were therefore examined in the light of a family of kinetic models, including the following modifications: substrate inhibition, porto-systemic shunting, and allosterism. The kinetic constants were assessed by iterative procedures, aiming at linearization of the double reciprocal plots. The two latter models were found to fit the experimental data by entering a shunting of 61% of the hepatic blood flow, or two active sites, respectively. Since this degree of shunting is improbable the results speak in favour of allosterism. The work gives an example of whole-liver kinetic considerations when simple Michaelis-Menten is insufficient.

Quantitative liver function and morphology after paracetamol administration to rats

The functional status of the liver after paracetamol administration to rats was dissociated with regard to cytosolic and microsomal functions. The cytosolic function, measured as galactose elimination capacity, was unchanged even after high doses of paracetamol. The microsomal function, measured as the prothrombin time, was reversibly decreased to a minimum 12 h after paracetamol administration and showed dose dependence. The structural changes of the liver cells were centrilobular necroses and dilatation of the endoplasmic reticulum. They were most marked 36 h after paracetamol and were not correlated to the functional impairment. We conclude that during acute paracetamol induced liver damage to rats different functions of the liver are unequally influenced and that the structural changes occur later than the functional ones. The paracetamol intoxicated rat is a promising model for further investigation of dissociation of subcellular functions during acute liver damage.

Impaired conversion of prednisone to prednisolone in patients with liver cirrhosis

Fourteen patients with liver cirrhosis received oral prednisone or prednisolone (0.3 mg per kg) randomised on two consecutive days. Serum prednisone and prednisolone were measured over the following four hours. Mean serum prednisolone concentration after oral prednisone decreased with impaired liver function estimated by galactose elimination capacity (r = 0.64, P less than 0.03). Mean serum prednisolone concentration after oral prednisone in the seven patients with severely impaired liver function was only 53% (P less than 0.05) of that observed in the seven patients with slightly impaired liver function. Conversely, mean serum prednisone concentration after oral prednisone in the patients with severely impaired liver function was 74% higher (P = 0.05) than in patients with slightly impaired liver function. Mean serum prednisolone after oral prednisolone was independent of liver function. As only prednisolone exerts glucocorticoid activity, our results indicate that prednisolone should be preferred to prednisone in the treatment of patients with impaired liver function.