Identification of B10, an alkaline phosphodiesterase of the apical plasma membrane of hepatocytes and biliary cells, in rat serum: Increased levels following bile duct ligation and during the development of cholangiocarcinoma

1. Administration of α-naphthylisothiocyanate (ANIT) to rats produced dose-dependent increases in plasma bile acid and bilirubin concentrations. Similar increases in plasma bile acid and bilirubin concentrations were evident in bile duct ligated rats, indicating that the severity of cholestasis is almost identical in both models. 2. Plasma alkaline phosphodiesterase I was increased by only 50–80% while alkaline phosphatase was increased more than threefold after ANIT administration. This is in contrast to an earlier study [S. R. Simpson, K. Rahman & D. Billington (1984) Clinical Science 67, 647–652] where, after bile duct ligation, serum alkaline phosphodiesterase I was elevated sixfold before any increase in alkaline phosphatase activity became apparent. Thus, plasma alkaline phosphodiesterase I does not offer as sensitive a marker of intrahepatic cholestasis (induced by ANIT) as it does of extrahepatic cholestasis (induced by bile duct ligation). 3. Hepatic alkaline phosphodiesterase I was unaffected by ANIT pretreatment while hepatic alkaline phosphatase was increased up to seven times. It is suggested that raised plasma alkaline phosphodiesterase I is due to regurgitation of the biliary enzyme rather than overspill of the enzyme from liver into blood. 4. Gel filtration showed that 24 h and 96 h after ANIT administration, rat serum contained a high molecular weight form of alkaline phosphodiesterase I, suggesting a different isoenzyme profile.

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Plasma Membrane Form of Phosphatidate Phosphohydrolase: A Possible Role in Signal Transduction during Liver Fibrogenesis

Clinical Science ◽

10.1042/cs0850281 ◽

1993 ◽

Vol 85 (3) ◽

pp. 281-287 ◽

Cited By ~ 5

Author(s):

Christopher P. Day ◽

Alastair D. Burt ◽

Ashley Stj. M. Brown ◽

Mark K. Bennett ◽

Desmond J. Farrell ◽

...

Keyword(s):

Plasma Membrane ◽

Liver Disease ◽

Bile Duct ◽

Common Bile Duct ◽

Alcoholic Liver Disease ◽

Bile Duct Ligation ◽

Sham Operation ◽

Common Bile Duct Ligation ◽

Duct Ligation ◽

Phosphatidate Phosphohydrolase

1. Several growth factors important in liver regeneration and fibrosis stimulate phospholipase D in plasma membranes via a receptor/G-protein-coupled mechanism resulting in hydrolysis of phosphatidylcholine to phosphatidate. Phosphatidate can be further hydrolysed to diacylglycerol by phosphatidate phosphohydrolase. Phosphatidate and diacylglycerol can act as ‘second-messengers’ and regulation of phosphatidate phosphohydrolase activity could control the balance between them. 2. A form of phosphatidate phosphohydrolase, located in the plasma membrane and insensitive to inhibition by N-ethylmaleimide, has recently been identified that is distinct from the ‘metabolic’ form, which is present in the cytosol and microsomes and is sensitive to N-ethylmaleimide. 3. We have investigated the hypothesis that the balance between regeneration and fibrosis is, in part, determined by the activity of plasma membrane phosphatidate phosphohydrolase through its effect on the phosphatidate/diacylglycerol ratio. N-Ethylmaleimide-insensitive and -sensitive phosphatidate phosphohydrolase activities were measured in three hepatic conditions characterized by regeneration and/or fibrosis: alcoholic liver disease in humans (regeneration and fibrosis) and rat livers after either acute CCl-4-induced injury (regeneration) or common bile duct ligation (fibrosis). 4. In patients with alcoholic liver disease, N-ethylmaleimide-insensitive phosphatidate phosphohydrolase activity was higher in cirrhotic biopsies (5.82±0.3 nmol of Pi min−1 mg−1 of protein, n = 19) than in non-cirrhotic biopsies (2.17 ±0.2, n = 23) or in wedge biopsies from healthy subjects undergoing routine cholecystectomy (2.16 ±0.5, n = 6). N-Ethylmaleimide-insensitive phosphatidate phosphohydrolase activity was unchanged in the 10 days after CCl4 treatment but increased progressively in common bile duct-ligated rats (e.g. day 28: ‘sham’ operation, 1.97 ±0.3, chronic bile duct ligation, 6.91 ±1.24 nmol of Pi min−1 mg−1 of protein). N-Ethylmaleimide-insensitive phosphatidate phosphohydrolase activity correlated closely with the degree of fibrosis in humans and rats. N-Ethylmaleimide-sensitive phosphatidate phosphohydrolase activity was unchanged after CCI4 treatment or common bile duct ligation and was not increased in cirrhotic livers. 5. Plasma membrane N-ethylmaleimide-insensitive phosphatidate phosphohydrolase increases in liver fibrosis but not regeneration. Stimulation of phosphatidate phosphohydrolase activity with its effect on the diacylglycerol/phosphatidate ratio may play a role in transduction of the fibrosis signal.

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Effect of Bile-Duct Ligation on Organelle Marker Enzymes in the Liver and Serum of Rats

Clinical Science ◽

10.1042/cs0480307 ◽

1975 ◽

Vol 48 (4) ◽

pp. 307-313

Author(s):

T. J. Peters ◽

G. Neale ◽

J. R. Heath

Keyword(s):

Endoplasmic Reticulum ◽

Plasma Membrane ◽

Bile Duct ◽

Enzyme Activities ◽

Liver Tissue ◽

Bile Duct Ligation ◽

Monoamine Oxidase A ◽

Mitochondrial Enzyme ◽

Marker Enzymes ◽

Duct Ligation

1. Marker enzymes for the principal subcellular organelles of rat liver were asayed in the liver of rats 1 day and 8 days after bile-duct ligation or after laparotomy as a control procedure. 2. The microsomal enzymes in liver tissue showed complex changes. Benz[α]pyrene hydroxylase activity, predominantly found in the smooth endoplasmic reticulum, was decreased. Glucose 6-phosphatase activity and ribonucleic acid, which are localized predominantly in the rough endoplasmic reticulum, were increased. 3. The plasma membrane enzyme, alkaline phosphatase, increased in activity after bile-duct ligation. 4. No changes in mitochondrial enzyme activities were noted after 1 day but there was a 50% reduction 8 days after ligation. Lysosomal enzyme activities did not change in the liver tissue. 5. Liver catalase and d-amino acid oxidase activities showed a slight increase at 1 day post-ligation but a significant fall by 8 days. 6. Lactate dehydrogenase, a cytosol enzyme, showed a decrease in activity after 1 day but an increase in tissue activities 8 days after ligation. 7. Serum activities of mitochondrial, plasma membrane, microsomal, lysosomal and cytosol marker enzymes tended to increase post-ligation, particularly at 8 days. 8. Monoamine oxidase, a predominantly mitochondrial enzyme, was greatly elevated in the serum after 1 day but had returned to normal activities by 8 days.

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Serum Alkaline Phosphodiesterase I in Experimental Biliary Obstruction in the Rat

Clinical Science ◽

10.1042/cs0670647 ◽

1984 ◽

Vol 67 (6) ◽

pp. 647-652 ◽

Cited By ~ 1

Author(s):

Stuart R. Simpson ◽

K. Rahman ◽

D. Billington

Keyword(s):

Alkaline Phosphatase ◽

Bile Duct ◽

Biliary Obstruction ◽

Bile Duct Ligation ◽

Serum Alkaline Phosphatase ◽

Gel Filtration ◽

Rat Serum ◽

Duct Ligation ◽

Rat Bile ◽

Molecular Weight Form

1. Alkaline phosphodiesterase I was present in rat liver at approx. 100-fold greater activity than alkaline phosphatase, and in rat bile at approx. 25-fold greater activity. 2. Rat serum alkaline phosphodiesterase I was increased 6-fold whilst serum alkaline phosphatase was increased only 2-fold 96 h after bile duct ligation. 3. In contrast to alkaline phosphatase, hepatic alkaline phosphodiesterase I was not affected by bile duct ligation, suggesting its raised serum activity was due to bile regurgitation rather than overspill of the enzyme from liver into blood. 4. Gel filtration showed that 8 and 96 h after bile duct ligation the serum contained a high molecular weight form of alkaline phosphodiesterase I. 5. It is suggested that alkaline phosphodiesterase I offers a potentially useful indicator of biliary obstruction in the rat.

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