Liver Amylase

Comparison of amylase mRNAs from rat parotid gland, pancreas and liver using reverse transcriptase-polymerase chain reaction

The expression of mRNA for amylase was examined using the reverse transcriptase-polymerase chain reaction (RT-PCR). An amylase product was strongly detected in parotid and pancreas, but less strongly in liver. The degree of identity between the PCR products was assessed by restriction-enzyme mapping using two restriction enzymes, EcoRI and ScaI, and DNA sequencing. The PCR product from pancreas was cut by both EcoRI and ScaI, while the products from parotid and liver were cut by EcoRI but not by ScaI. The sequence of the parotid product was 90.4% homologous to that of the pancreas, and 100% homologous to that of the liver. These results indicate that the same amylase mRNA may be expressed in parotid and liver. In addition, the expression of amylase mRNAs in other rat tissues was investigated using RT-PCR, and the sensitivity of each PCR product to ScaI was tested. A weak single band was detected in submandibular gland, sublingual gland and stomach. ScaI digestion cut the stomach product into two fragments, but had no effect on the submandibular and sublingual products. Thus, it may be possible to classify amylase isoenzymes into pancreatic and parotid types based on the sensitivity of their PCR products to ScaI.

Expression of alpha-amylase gene in rat liver: liver-specific amylase has a high affinity to glycogen

The reactivity of rat liver alpha-amylases with maltotriose (G3), maltopentose (G5) and glycogen has been investigated. Liver amylases were found to be glycosylated and to have a molecular mass of 50 kDa by Western blotting using an anti-human salivary amylase antibody. The glycosylated liver amylases were found to be capable of G3- and G5-hydrolysis and of glucose formation, as demonstrated by thin-layer chromatography. When the amylase preparation was exposed to different concentrations of glycogen and run on a cellulose acetate membrane, the mobilities of rat liver amylases significantly decreased with tailing directly from the point of origin. In contrast, rat salivary amylases were not so much. These results indicate that rat liver amylases have a strong affinity to glycogen. We confirmed the expression of liver-specific amylases in rat liver by reverse transcriptional-polymerase chain reaction (RT-PCR); PCR products showed one band of an expected size of 474 bp using primers tested in the present study. A partial nucleotide sequence was then determined. When compared with the gene of mouse liver amylase, the substitution of 26 bases out of 434 bases was elucidated. The present data demonstrate the presence of liver-specific amylases in rats.

Serum amylase of non-parotid and non-pancreatic origin increases on feeding in rats and may originate from the liver

1. In order to evaluate possible non-salivary contributions to the content of salivary-type amylase in the circulation, parotid glands--the only salivary source of amylase in rats--have been totally removed and the effects on serum amylase have been assessed, after fasting and at different times after feeding. 2. Despite the parotidectomy the resting level of salivary-type amylase remained the same and an increase was still found to occur on feeding. 3. Isoelectric focusing has identified additional isoforms of amylase in serum and liver distinct from those occurring in parotid saliva. 4. The liver therefore may be contributing to the fasting levels of serum amylase and to the increases that occur on feeding, in rats.

Serum amylase and isoamylase values in dogs with pancreatic disease

Serum amylase and isoamylase values were determined in three groups of dogs. The first group contained control dogs while the other groups contained dogs with confirmed exocrine pancreatic insufficiency and diabetes mellitus respectively. The trypsin-like immunoreactivity test was also carried out on sera from dogs with exocrine pancreatic disease (EPI). A significant difference was detected in the serum amylase values between the three groups which may be of limited diagnostic value. Dogs with EPI had values lower than normal while those with diabetes mellitus had values higher than control dogs. No evidence of exocrine pancreatic insufficiency was found in dogs with diabetes mellitus.

Effects of secretory nerve stimulation on the movement of rat parotid amylase into the circulation

Stimulation of the nerves to the rat parotid gland demonstrated that increases in serum amylase levels can originate exclusively from this gland. However, whilst parasympathetic nerve stimulation caused a significant movement of parotid amylase into the blood, sympathetic nerve stimulation did not, despite the higher concentration of amylase in the saliva evoked. Experiments in which conscious animals were fed for a short period showed that parotid amylase reaches the blood during normal activity. The mechanisms underlying the movement of parotid amylase into the circulation are still unknown but there appears to be some dependence on the volume of saliva being produced.

Ectopic production of salivary-type amylase by a IgA-lambda-type multiple myeloma

A patient with IgA-lambda-type multiple myeloma who appeared to be secreting salivary-type amylase ectopically is reported. Both the patient's serum and urine contained high levels of amylase. Amylase activity in the supernatant of cultured myeloma cells, obtained from the patient's pleural effusion while he had malignant pleuritis, increased almost linearly from the time of cell seeding. The presence of IgA and S-type amylase in the myeloma cells was demonstrated cytochemically and by immunoelectron microscopy. These observations showed that amylase was produced by these human myeloma cells.

Hyperamylasemia and S-type isozyme dominance in liver cirrhosis

To investigate the mechanisms of serum amylase abnormalities in liver disease, we determined serum amylase levels, S-type isozyme proportion, clinical symptoms, and laboratory data in 38 cases of histologically confirmed liver cirrhosis and 19 controls. Of the 12 patients who were hyperamylasemic (12/38, 32%), 5 showed S-type isozyme dominance (5/12, 42%), whereas in the 26 normoamylasemic cirrhosis patients, only 5 were S-type isozyme dominant (5/26, 19%). Isozyme percentages were significantly higher (P less than 0.01) in the dominant-S-type cases than in the controls, and S-type dominance was found more frequently in the hyperamylasemic than in the normoamylasemic cirrhosis cases. Only ascites and esophageal varices were observed more frequently as clinical symptoms in the dominant-S-type cases. Our results suggest that amylase is not produced in the human liver, but that the decreased clearance rate of amylase, especially the S-type isozyme, may be a cause of hyperamylasemia and S-type isozyme dominance in cirrhosis.

Structural and functional integrity of rat liver perfused in backward and forward directions

The purpose of this study was to assess if reversal of the direction of isolated rat liver perfusion would cause significant alterations in hepatic functions and structure. Five isolated rat livers were perfused forward and another five backward with oxygenated Ringer's solution for up to 90 min (hydrostatic pressure: less than or equal to 13 cm H2O; flow rate: forward 3.88 +/- 0.34 ml/min per gram and backward 3.76 +/- 0.34 ml/min per gram). At the end of the experiment, livers were perfusion-fixed for morphological examination. The following results were obtained: No significant differences were noted between the forward and backward perfusions with respect to oxygen uptake, mean bile flow (forward 0.57 +/- 0.12; backward 0.60 +/- 0.14 ml/min per gram), average bile acid excretion (forward 2.39 +/- 1.11; backward 2.83 +/- 0.94 nmol/min per gram), hydroxylation pattern of bile acids, urea synthesis, release of lactic dehydrogenase, glucose secretion, and redox ratios. Light and electron microscopy, including morphometry of parenchymal and sinusoidal areas, revealed that the backward perfusion caused a greater degree of sinusoidal distension, but no other noteworthy differences. Hepatic ultrastructure was well preserved. We conclude that reversing the direction of perfusion does not alter structure and major hepatic functions significantly.

Chromatin structure and expression of amylase genes in rat pituitary tumor cells

Amylase-coding sequences were detected in the population of cytoplasmic RNA molecules from cultured rat pituitary GH3 cells. The amylase genes in these cells are in a micrococcal nuclease-sensitive, transcriptionally active chromatin conformation. The amount of cytoplasmic amylase mRNA appears to be controlled by small molecules provided by the fetal calf serum component of the culture medium.

Pancreas-specific genes: structure and expression

Via recombinant DNA technology the mRNA sequence of pancreatic amylase has been cloned and its nucleotide sequence has been determined. The cloned sequence represents 96% of the total length of amylase mRNA; missing are an estimated 75 +/- 30 nucleotides from the 5' end. The amino acid sequence of rat pancreatic amylase was deduced solely from the nucleotide sequence of the mRNA. Unlike other eukaryotic mRNAs, the amylase mRNA has short 5' and 5' untranslated regions, suggesting that long untranslated regions of eukaryotic mRNAs either do not contain extensive functional sequences or that these sequences are incorporated within the amino acid coding region of amylase mRNA. The cloned amylase mRNA sequence was radiolabeled and used as a probe for in situ hybridization. These experiments demonstrate that amylase mRNA is present in all acinar cells but not in other pancreatic cell types. Using the cloned amylase mRNA sequences as a hybridization probe, three nonoverlapping genomic DNA fragments containing amylase gene sequences were isolated. From the similar sequence organization of the three amylase genes visualized by DNA heteroduplex mapping, a consensus structure of a rat amylase gene is proposed. It is an extended gene structure 10 kilobase pairs in length containing the 1547 base pairs of the cloned mRNA coding sequence interrupted by seven intervening sequences ranging from 400-2000 base pairs long. Thus, in nuclear DNA the amylase mRNA coding sequence is disrupted into at least eight segments from 150-300 base pairs long.

Mouse liver and salivary gland alpha-amylase mRNAs differ only in 5' non-translated sequences

The sequence of 1,773-nucleotide major and 1,806-nucleotide minor mouse liver alpha-amylase mRNAs differ only with respect to approximately 30 additional residues at the extreme 5' terminus of the minor species. Comparison of the liver alpha-amylase mRNAs with their salivary gland counterpart reveals that these mRNAs share identical coding and 3'-noncoding sequences, but contain distinct 5'-terminal residues. These data suggest that all three mRNAs might be transcribed from the same gene.

Structure of a family of rat amylase genes

The sequences of two cloned rat pancreatic amylase cDNAs comprising 95% of the mRNA sequence are reported. Analysis of cloned rat genomic DNA fragments using cloned cDNA probes indicates that the rat genome contains multiple closely related amylase genes in which the cDNA sequences are distributed within a region 9 kilobases in length and are interrupted by at least seven intervening sequences.

Amylase levels in the tissues and body fluids of the domestic cat (Felis catus)

1. The amylase activities of serum, liver, pancreas, submaxillary and parotid glands, saliva, duodenum, colon, lung, heart, spleen, kidney and skeletal muscle of the domestic cat, were determined. 2. As in most mammals, the highest amylase content was found in the pancreas. Levels in saliva and salivary glands were very low. 3. Amylase activities of the serum, liver and pancreas have an optimum pH 7.0-7.5. 4. Amylases of serum, liver and pancreas were inactivated by removal of chloride and these activities mainly restored by addition of chloride.

Amylase thermolability in body fluids

The thermolability of amylase was measured in saliva, pancreatic juice, urine, adult and neonatal sera. The mean percentage thermolability from these fluids was 100%, 99%, 87%, 44% and 23% respectively. In patients with acute pancreatitis and mumps the amylase was 84% and 83% thermolabile during the acute phase. On resolution of the pancreatitis this dropped towards normal. Patients with a pancreatic pseudocyst showed a high mean percentage thermolability (82%). These results could suggest that a component of amylase in human serum is not of pancreatic or salivary origin. In addition, this simple technique may be helpful in the diagnosis of pancreatic pseudocyst.

Electrophoretic and immunological properties of liver alpha-amylase of well-fed and fasted rats

1. Alpha-Amylase (1,4-alpha-D-glucan glucanohydrolase, EC 3.2.1.1) in the liver of well-fed rats showed a characteristic electrophoretic mobility between those of pancreatic and parotid amylases. Amylase in the liver of fasted rats showed an electrophoretic mobility identical to that of parotid amylase. When fasted rats were re-fed on a standard diet for two days the electrophoretic mobility of their liver amylase returned to that of the liver amylase of well-fed rats. 2. When purified rat pancreatic and parotid amylases were mixed with a final concentration of 4% glycogen solution, their electrophoretic mobilities both became similar to that of liver amylase of well-fed rats. The electrophoretic mobility of glycogen corresponded to that of liver amylase of well-fed rats. Since liver amylase of fasted rats has the same mobility as parotid amylase and serum contains only parotid-type amylase, these findings suggest that liver amylase of well-fed rats may be a complex of serum amylase and glycogen. 3. The antigenicities of the liver amylases of well-fed and fasted rats were the same as that of purified parotid amylase, but different from that of purified pancreatic amylase. Amylase in serum and urine, which had the same electrophoretic mobility as parotid amylase, had the same antigenicity as purified parotid amylase and the liver amylases of well-fed and fasted rats.