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Glucocorticoids increase amylase mRNA levels, secretory organelles, and secretion in pancreatic acinar AR42J cells.

Previous studies have suggested a role for glucocorticoids in the differentiation of the acinar pancreas. We have now used the rat tumor cell line AR42J, derived from the acinar pancreas, to directly study this effect of glucocorticoids in vitro. The steroid hormones dexamethasone, corticosterone, aldosterone, and progesterone, but not estrogen, increased both the amylase content and the number of secretory granules of these cells. The potencies of the steroids were directly related to their effectiveness as glucocorticoids; dexamethasone was the most potent hormone and gave maximal effects at 100 nM. Morphometric analyses revealed that dexamethasone increased the volume density of granules 5.5-fold from 0.20 +/- 0.08 to 1.10 +/- 0.20% (n = 4) of the cytoplasmic volume. Dexamethasone treatment also increased the volume density of rough endoplasmic reticulum 2.4-fold from 1.20 +/- 0.09 to 2.86 +/- 0.30% (n = 5) of the cytoplasmic volume. After 48 h of dexamethasone treatment the cellular content of amylase increase eightfold from 2.8 +/- 0.4 to 22.6 +/- 3.8 U/mg protein (n = 6). This effect of dexamethasone was discernible after 12 h of incubation and approached maximal stimulation after 72 h of incubation. The increases in cellular amylase content were due to increased amylase synthesis as shown by specific immunoprecipitation of [35S]methionine-labeled proteins. Moreover, in vitro translation of cellular mRNA indicated that dexamethasone treatment increased amylase mRNA. Dexamethasone treatment also led to increased secretion of amylase in response to the secretagogue cholecystokinin. These data indicate, therefore, that glucocorticoids induce a more highly differentiated phenotype in AR42J pancreatic cells, and they suggest that glucocorticoids act via the enhanced transcription of specific mRNAs for acinar cell proteins.

Aldosterone↗

Variation in activities of amylase allozymes associated with chromosome inversions in Drosophila pseudoobscura, D. persimilis and D. miranda.

Different electrophoretic alleles of amylase show associations with particular chromosome 3 inversions in D. pseudoobscura and D. persimilis. Relative adult amylase activities were compared in 37, 37 and 10 strains of D. pseudoobscura, D. persimilis and D. miranda, respectively. Strains carrying the same electrophoretic allele were compared by crossing these lines individually to a reference strain carrying a different electrophoretic mobility allele. This procedure allows comparisons among species, inversions, electromorphs and strains for genetic variation in amylase activity. F2 analysis established that the activity variation co-segregates with the structural amylase locus. This type of variation could be due to either structural gene differences or differences in closely linked, cis-acting regulatory regions. Variation has been detected among and within electrophoretic mobility classes. Moreover, this variation is clearly nonrandom and reveals more of the genetic structure associated with the chromosomal inversion phylogeny of D. pseudoobscura and D. persimilis. ----Some of the findings are: (1) Similar electromorphs in D. pseudoobscura and D. persimilis usually show different activities. These species show nearly complete differentiation of amylase alleles, based on activities. (2) D. persimilis has the broadest range of variation in amylase activity, about four-fold between the highest and lowest alleles. D. pseudoobscura and D. miranda are also polymorphic for activity, but have more constrained ranges of variation. D. miranda alleles show on the average about four times the activity of D. pseudoobscura alleles. (3) Some association of electrophoretic mobility and activity has been found. Alleles 1.09 of D. persimilis, as well as 1.43 and 1.55 of D. miranda, have relatively high activity. It may be that these high activity alleles are part of an adaptation to cooler habitats. (4) Within electrophoretic classes, associations of activities with inversions have been found. These are especially strong in D. persimilis. The 1.00 alleles in the ST, KL, MD and WT inversions, the 0.92 allele in the ST and MD inversions and the 1.09 allele in the WT and KL inversions have levels of activities that depend upon the arrangement in which they are located. These results demonstrate that suppression of recombination in inversion heterokaryotypes can result in extensive genic divergence between inversions.

Amylases↗

The binding of VIP36 and alpha-amylase in the secretory vesicles via high-mannose type glycans.

Vesicular integral protein of 36 kDa (VIP36) is an intracellular lectin recognizing high-mannose type glycans and is highly expressed in salivary glands, especially the parotid gland, which secretes alpha-amylase in large quantities. Here immunoelectron microscopy demonstrated that VIP36 was primarily localized to secretory vesicles in the glandula parotis of the rat, where alpha-amylase also resided. A secretory vesicle fraction, prepared by Percoll density gradient centrifugation, contained both VIP36 and alpha-amylase. Moreover, alpha-amylase that was localized to these secretory vesicles contained high-mannose type glycans. In addition, VIP36 coprecipitated with alpha-amylase in an endo H treatment-sensitive manner. These results suggest that VIP36 is involved in the secretion of alpha-amylase in the rat parotid gland.

Animals↗

Evolutionary rearrangement of the amylase genomic regions between Drosophila melanogaster and Drosophila pseudoobscura.

Two Drosophila pseudoobscura genomic clones have sequence similarity to the Drosophila melanogaster amylase region that maps to the 53CD region on the D. melanogaster cytogenetic map. The two clones with similarity to amylase map to sections 73A and 78C of the D. pseudoobscura third chromosome cytogenetic map. The complete sequences of both the 73A and 78C regions were compared to the D. melanogaster genome to determine if the coding region for amylase is present in both regions and to determine the evolutionary mechanism responsible for the observed distribution of the amylase gene or genes. The D. pseudoobscura 73A and 78C linkage groups are conserved with the D. melanogaster 41E and 53CD regions, respectively. The amylase gene, however, has not maintained its conserved linkage between the two species. These data indicate that amylase has moved via a transposition event in the D. melanogaster or D. pseudoobscura lineage. The predicted genes within the 73A and 78C regions show patterns of molecular evolution in synonymous and nonsynonymous sites that are consistent with previous studies of these two species.

Amylases↗

Dietary carbohydrate source and energy intake influence the expression of pancreatic alpha-amylase in lambs.

In ruminants, pancreatic alpha-amylase is the primary enzyme responsible for the initial hydrolysis of alpha-linked glucose in the small intestinal lumen. The objective of this experiment was to examine the effects of altered dietary starch and energy supply on the expression of pancreatic alpha-amylase mRNA, protein and activity in lambs. Wether lambs (n = 24; 28 +/- 0.5 kg body weight) were fed low or high starch diets at 1.2 or 1.8 x net energy of maintenance for at least 28 d before tissue collection. Lambs fed the high energy/high starch diet tended to have more pancreatic alpha-amylase protein (54.5 kDa; P: = 0.08) and had greater activity (P: = 0.03), but alpha-amylase mRNA (1.6 kb) tended to be lower (P: = 0.17). Additionally, rumen fluid total short-chain fatty acid concentration was greater (P: = 0.04) and plasma glucose concentration tended to be greater (P: = 0.07) in lambs fed the high energy/high starch diet. However, pancreatic trypsinogen protein (25. 5 kDa) and jejunal maltase activity were not influenced by dietary treatment, suggesting that different regulatory systems are involved in regulating the tissue protein or activity levels of these two enzymes compared with alpha-amylase. These data suggest that dietary regulation of pancreatic alpha-amylase expression in ruminants is complex and probably regulated by transcriptional and post-transcriptional events.

Animals↗

Evidence for the involvement of cAMP-dependent protein kinase in the exocytosis of amylase from parotid acinar cells.

To determine the role of cAMP-dependent protein kinase in the exocytosis of amylase from rat parotid acini, I studied the effects of various cAMP analogues on amylase release and protein phosphorylation in saponin-permeabilized parotid cells. The dose-dependent responses of amylase release and protein phosphorylation evoked by cAMP, dibutyryl-cAMP, and 8-chlorophenylthio-cAMP were closely correlated. Furthermore, when the permeabilized cells were incubated with a combination of site-selective cAMP analogues, such as N6-benzoyl-cAMP plus 8-thiomethyl-cAMP (RII-directed) or N6-benzoyl-cAMP plus 8-aminohexylamino-cAMP (RI-directed), synergistic stimulation of amylase release was clearly observed. As reported previously [T. Takuma (1988) Biochem. J. 256, 867-871], however, the protein phosphorylation evoked by 8-chlorophenylthio-cAMP was markedly inhibited by H-8 without a significant decrease in amylase release. These results suggest that cAMP-dependent protein kinase is involved in the regulation of amylase exocytosis, although the role of its catalytic subunit is still uncertain.

Amylases↗

Detection of human urinary alpha-amylase encoded by the AMY2B gene using a fluorogenic substrate, FG5P.

The existence of alpha-amylase (HXA) encoded by alpha-amylase gene AMY2B in healthy humans was examined using a fluorogenic substrate, FG5P (FG-G-G-G-G-P: FG, 6-deoxy-6-[(2-pyridyl)amino]-D-glucose residue; G, glucose residue; P, p-nitrophenyl residue; -, alpha-1,4-glycosidic bond). Chromatofocusing of urine from a healthy human was carried out. FG5P was digested with the fractions exhibiting alpha-amylase activity and each digest at an early stage was analyzed by HPLC. FG5P was hydrolyzed to FG3 (FG-G-G) and p-nitrophenyl alpha-maltoside (G-G-P), and to FG4 (FG-G-G-G) and p-nitrophenyl alpha-glucoside (G-P). The molar ratios of FG4 to FG3 (FG4/FG3) in the digests with basic fractions were larger than those in the digests of human pancreatic alpha-amylase (HPA, 1.11) and human salivary alpha-amylase (HSA, 0.51). Considering that the value for the AMY2B gene product with yeast (yHXA) is 1.88, a value of more than 1.11 implies that HXA exists. The amount of HXA was determined after removal of HSA on an anti-human salivary alpha-amylase antibody bound column. The FG4/FG3 values for six urine samples free from HSA were 1.23-1.26. Assuming that the FG4/FG3 value for HXA is the same as that for yHXA, the ratios of HXA and HPA were estimated to be 1:5.4-4.1. The results obtained showed that the AMY2B gene is usually expressed as HXA in healthy humans.

Carbohydrate Sequence↗

The role of SH and S-S groups in Bacillus cereus beta-amylase.

The properties of sulfhydryl (SH) and disulfide (S-S) groups in Bacillus cereus BQ10-S1 Spo III beta-amylase have been investigated to clarify their roles in the enzyme action. Two out of three cysteine residues in B. cereus beta-amylase were found to form an S-S bond, which was found to be located between Cys91 and Cys99 by the analysis of an S-S containing peptide. The replacement of the soybean beta-amylase model around L3 loop 1 revealed that the S-S bond is located at the root of this flexible loop that moves between open and closed forms during catalysis. The analysis of fluorescence labeled peptides revealed that the remaining free SH group was Cys331. Modification of Cys331 with N-ethylmaleimide or p-chloromercuribenzoic acid (PCMB) caused inactivation of the enzyme. The rate constants for the reactions were consistent with those of Cys343 in soybean enzyme. The binding affinity of the PCMB-modified enzyme to maltose was also decreased. These results indicate that the modification of Cys331, which exists as a free SH group in B. cereus beta-amylase caused inactivation by a similar mechanism to that in the case of Cys343 in soybean beta-amylase as assumed from the sequence homology. This cysteine residue has a common role in beta-amylases irrespective their origin.

Bacillus cereus↗

Changes in the properties and molecular weights of Bacillus subtilis M-type and N-type alpha-amylases resulting from a spontaneous deletion.

The regulatory gene, amyR2, and the structural gene, amyEn+, coding for N-type alpha-amylase from Bacillus subtilis N7 have been cloned in the B. subtilis plasmid pUB110. The complete nucleotide sequence of amyR2 and amyEn+ has been determined. Starting from an ATG initiator codon, there was an open reading frame comprising 477 amino acids (1,431 bp), giving a molecular weight of 52,678. The NH2-terminal portion of amyEn+ encoded a 41-amino acid-long signal sequence. The DNA nucleotide sequence was compared with the sequences of amyEm+ coding for M-type alpha-amylase from B. subtilis NA64 (Yamazaki et al. (1983) J. Bacteriol. 156, 327-337) and another B. subtilis alpha-amylase gene (Yang et al. (1983) Nucl. Acids Res. 11, 237-249). Almost all the sequences were identical in the three genes. However in the sequence of amyEn+ 32 bp of the other two alpha-amylase genes were deleted in the region from nucleotide 1,406 to 1,437. This deletion region was included in the direct repeat structure of the two genes. The reading frame downstream of the deletion region of amyEn+ shifted and a new termination codon (TGA) appeared at 26 bp downstream. Thus, the differences of the M-type and N-type alpha-amylases from amyEm+ and amyEn+ seemed to be caused by the occurrence of translation termination at different sites of the alpha-amylase gene.

Bacillus subtilis↗

Preparation of human salivary alpha-amylase specific monoclonal antibody.

A mouse hybridoma cell line which produced an anti-human salivary alpha-amylase monoclonal antibody was obtained by fusion between mouse spleen cells immunized with human salivary alpha-amylase and mouse myeloma cells, followed by screening the hybridoma cells by enzyme-linked immunosorbent assay. The hybridoma cell line (27-4-1) secreted IgG. The monoclonal antibody produced by the hybridoma showed no inhibitory effect on the activity of human salivary alpha-amylase. The specificity and reactivity of this monoclonal antibody were examined by determining the activities of human salivary and pancreatic alpha-amylases bound to the monoclonal antibody immobilized on polystyrene balls or by enzyme immunoassay with the monoclonal antibody conjugated with beta-D-galactosidase. The results revealed that the monoclonal antibody produced by the hybridoma cell line was specific for salivary alpha-amylase and absolutely unreactive to pancreatic alpha-amylase.

Antibodies, Monoclonal↗

Inhibition of growth of Aspergillus flavus and fungal alpha-amylases by a lectin-like protein from Lablab purpureus.

Aspergillus flavus is a fungal pathogen of maize causing an important ear rot disease when plants are exposed to drought and heat stress. Associated with the disease is the production of aflatoxins, which are a series of structurally related mycotoxins known to be carcinogenic. Previous research has suggested that the alpha-amylase of A. flavus promotes aflatoxin production in the endosperm of infected maize kernels. We report here the isolation and characterization of a 36-kDa alpha-amylase inhibitor from Lablab purpureus (AILP). AILP inhibited the alpha-amylases from several fungi but had little effect on those from animal and plant sources. The protein inhibited conidial germination and hyphal growth of A. flavus. The amino acid sequence indicated that AILP is similar to lectin members of a lectin-arcelin-alpha-amylase inhibitor family described in common bean and shown to be a component of plant resistance to insect pests. AILP also agglutinated papain-treated red blood cells from human and rabbit. These data indicate that AILP represents a novel variant in the lectin-arcelin-alpha-amylase inhibitor family of proteins having lectin-like and alpha-amylase inhibitory activity.

Aflatoxins↗

Amylase levels in ascitic fluid.

The amylase concentration of ascitic fluid and serum were measured in patients with various types of ascites to determine their normal range. The mean (+/- SD) nonpancreatic ascites amylase concentration was 42 +/- 44 IU/L (range 4-234) and the mean ascitic fluid/serum amylase concentration ratio was 0.44 +/- 0.33 (range 0.10-1.55). Of the various types of non-pancreatic ascites (sterile cirrhotic, infected, malignant, etc.), no group had a significantly different ascitic fluid amylase concentration or concentration ratio than any other group. Two patients with pancreatic ascites had a mean ascitic fluid amylase concentration of 1,957 +/- 1,093 IU/L and a mean amylase concentration ratio of 5.59 +/- 0.02--both significantly (p less than 0.001) greater than those of nonpancreatic ascites.

Amylases↗

Amylase in human milk from mothers of preterm and term infants.

Amylase activity and isoenzyme pattern were determined in preterm human milk from 25 mothers during the first 55 days after delivery and from 25 mothers delivered at term. The diurnal variation in amylase activity and the variation during a feeding were studied in two mothers. There is a high amylase activity in preterm colostrum, which slowly decreases during the first 2 months. The individual variation in amylase activity is considerable. There is no difference in amylase activity in preterm and term human milk. The isoamylase of preterm milk is of the salivary type, just as in term milk. There is no great variation in amylase activity during a feeding or from one feeding to another.

Amylases↗

Asynchronism between amylase secretion and packaging in the zymogen granules of pig pancreas.

By pulse and chase experiments with [3H]leucine we have followed the time-course packaging of newly synthesized amylase in the zymogen granules of pig pancreas in vivo. In parallel, with a second group of pigs, we have followed the time-course release of newly synthesized amylase. The ratios of specific radioactivities of amylase in the zymogen granule over that of the homogenate indicated that substantial amounts of newly synthesized amylase had already reached the zymogen granule compartment at 50-min postpulse. Specific radioactivity increased up to 180 min, then a plateau was obtained. In the juice with the other group of pigs, starting at 40 min postpulse, amylase specific radioactivity increased up to about 100 min, then slowly decreased in the next hours. These results show an asynchronism between packaging of newly synthesized amylase in the zymogen granule compartment and its release in the juice under resting conditions, supporting the concept of a partial bypass of the zymogen granule compartment.

Amylases↗

Correlation of serum amylase levels with pancreatic pathology and pancreatitis etiology.

Fifty-one patients, 35 men and 16 women, with acute pancreatitis were studied prospectively with early computed tomography (CT). Etiological factors for acute pancreatitis were alcohol abuse (n = 28), gallstones (n = 14), pancreas cancer (n = 3) and miscellaneous (n = 6). Admission serum amylase levels ranged between 68-5,856 U/L with a mean of 1,090 +/- 1,369 U/L. The mean serum amylase level was significantly different between patients with alcoholic pancreatitis (439 +/- 302 U/L) and gallstone pancreatitis (2,480 +/- 1,575) (p less than 0.001). The initial pancreatic CT findings and corresponding mean serum amylase levels were in CT grade A (pancreas normal) 1,499 +/- 1,569 U/L (n = 11), in CT grade B (pancreatic enlargement with inflammation confined to pancreas) 1,144 +/- 1,542 U/L (n = 18), in CT grade C (inflammatory extension into one peripancreatic space) 722 +/- 962 U/L (n = 13) and in CT grade D (inflammatory extension into two or more peripancreatic spaces) 590 +/- 369 U/L (n = 9). However, on separating the etiology subgroups, there was no increase or decrease in the serum amylase level with increasing pancreatic inflammatory involvement. Pancreatic complications (pseudocyst, abscess, necrosis) requiring surgical intervention developed only in patients with CT grades C and D. We conclude that within the etiologic subgroups there is no correlation between the initial serum amylase level and the extent of pancreatic involvement visualized by CT. These findings provide a pathological basis for the clinical observation that the initial serum amylase level cannot predict the outcome in acute pancreatitis.

Acute Disease↗

Selectivity of quercetin inhibition on stimulated amylase release in rat pancreatic acini.

Quercetin (Q) has been shown to inhibit Ca2+-dependent processes. The present study evaluates the effect of Q on amylase release stimulated by various agonists in dispersed rat pancreatic acini. Q inhibited amylase release stimulated by an optimal concentration of carbachol. The inhibition was dependent on Q concentration. Preincubation with Q was not necessary. Maximal inhibition (up to 60% of control) was reached at 50 microM of Q and was completely reversible. Full responsiveness of the acini to agonist stimulation was reestablished as early as 5 min upon the removal of Q. At 50 microM, Q inhibited stimulated amylase release by optimal concentrations of tetradecanoylphorbol-13-acetate (TPA) (10(-6) M), A23187 (3 x 10(-6) M), cholecystokinin C-terminal octapeptide (CCK-OP) (10(-9) M) and carbachol (3 x 10(-6) M), but not by vasoactive intestinal polypeptide (VIP) (3 x 10(-7) M). Instead, Q promoted amylase release stimulated by VIP. The inhibition of amylase secretion by Q occurred only at near optimal, optimal, and supraoptimal concentrations of TPA, A23187, CCK-OP, and carbachol. The potentiation effect of Q on VIP-stimulated amylase secretion was, however, seen at all concentrations of VIP used (10(-8) to 10(-6) M). Quercetin also inhibited protein kinase C activity from rat pancreas in a dose-dependent manner. Maximal inhibition (approximately 85%) was seen at 100 microM of Q. These results provide further support that the intermediary steps for stimulated enzyme secretion in pancreatic acini by TPA, A23187, CCK-OP, and carbachol involve calmodulin and/or protein kinase C, whereas VIP does not.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylases↗

Reversal by glucose of pancreatic amylase insufficiency in chronic alcoholic rats.

Carbohydrate consumption regulates pancreatic amylase synthesis in rats. The Lieber-DeCarli 36% alcohol diet employed in chronic alcohol studies and the isocaloric control diet contain 11 and 47% of total calories from carbohydrates, respectively. Young rats fed ad libitum the 36% ethanol diet for 2 weeks obtained 1.2 g/day of carbohydrate, whereas those pair-fed with control diet received 5.8 g/day. Rats fed the 36% ethanol diet and given an intramuscular injection of a solution of 1.5 g of glucose daily for 2 weeks received twofold greater amounts of carbohydrate than saline-injected controls (2.7 versus 1.2 g). These changes in carbohydrate intake produced proportionate changes in pancreatic amylase levels. The secretory responses to cholecystokinin-octapeptide (CCK8) of acini from control and glucose-injected rats were significantly higher compared with those in the saline-injected or noninjected alcohol groups. The blood alcohol levels in glucose-injected rats were markedly reduced compared with other alcohol groups (71.7 versus 274.9 mg/dl) despite similar amounts of ethanol ingestion daily (2.4 g) in the three groups. In vitro experiments with acini from rats fed a nutritionally optimal diet revealed that high pharmacologic concentrations of ethanol, while inducing basal secretion, inhibited CCK8-stimulated amylase secretion. These results indicate that: (a) the amount of alcohol consumption does not correlate with either the levels of blood alcohol or of pancreatic amylase; (b) the carbohydrate availability in rats regulates pancreatic amylase levels despite significant levels of alcohol in blood; (c) blood alcohol levels observed in vivo may not affect synthetic and secretory processes of amylase in pancreatic acini.

Alcoholism↗

[D-Ala1, Leu9-psi-CH2NH-Leu10]neuromedin C antagonizes neuromedin C-stimulated amylase release by acini isolated from the rat pancreas.

Two novel neuromedin C analogs [D-Ala1, Leu9-psi-CH2NH-Leu10]neuromedin C and [Leu9-psi-CH2NH-Leu10]neuromedin C, were synthesized by rapid solid phase methods and examined for their abilities to inhibit neuromedin C-stimulated amylase release by isolated rat pancreatic acini. Both analogs significantly inhibited maximally stimulated amylase release by neuromedin C in a dose-dependent manner with maximal inhibition seen at concentrations of 100 and 300 microM of [D-Ala1, Leu9-psi-CH2NH-Leu10]neuromedin C and [Leu9-psi-CH2NH-Leu10]neuromedin C, respectively. The IC50 (concentration required to half-maximally inhibit neuromedin C-stimulated amylase release) was 1.5 microM for [D-Ala1, Leu9-psi-CH2NH-Leu10]neuromedin C compared to a 13.4 microM IC50 for [Leu9-psi-CH2NH-Leu10]neuromedin C. The [D-Ala1, Leu9-psi-CH2NH-Leu10]neuromedin C analog produced a parallel rightward shift in the neuromedin C dose-response curve and Schild plots of the inhibition data gave a slope of 0.969 +/- 0.121 and a pA2 (apparent affinity for the acinar cell receptor in terms of neuromedin C receptor-stimulated amylase release) of 100 nM. While [D-Ala1, Leu9-psi-CH2NH-Leu10]neuromedin C significantly inhibited both neuromedin B- and gastrin releasing peptide-stimulated amylase release, the analog did not inhibit amylase release in response to either cholecystokinin octapeptide, vasoactive intestinal peptide, substance P, carbamylcholine, the Ca2+ ionophore A23187, forskolin, or 8-bromo-cyclic AMP. The results demonstrate that [D-Ala1, Leu9-psi-CH2NH-Leu10]neuromedin C is a potent, specific, and competitive antagonist for neuromedin C and peptides of the gastrin releasing peptide family and may serve as a useful molecule for exploring the physiological role of these peptides.

Amino Acid Sequence↗