Enhancement in gastric mucosal laminin receptor expression with ulcer healing by sucralfate

The expression of gastric mucosal laminin receptor during chronic ulcer healing in the presence of sucralfate treatment was investigated. Rats with induced gastric ulcers were treated twice daily for 20 consecutive days either with sucralfate at 100mg/kg or vehicle, and at different stages of treatment used for gastric mucosal laminin receptor quantitation. The assays revealed that accelerated ulcer healing (8 days) in the presence of sucralfate was accompanied by a significant enhancement in the laminin receptor expression. A 2.8-fold increase in the receptor expression over that of controls occurred by the 3rd day of sucralfate treatment, reached a maximum of 3.1-fold increase by the 7th day and remained elevated even after 20 days of treatment. The results attest to the ability of sucralfate to stimulate and promote the events associated with gastric mucosal integrity restoration.

Enhancement of gastric mucus phospholipid secretion by an antiulcer agent, ebrotidine

1. Rat gastric mucosal cells, subjected to phospholipid labeling by incubating the cell suspension in DMEM with [3H]choline, were exposed to different concentrations (0-150 microM) of H2-receptor antagonists, ebrotidine and ranitidine, and the phospholipid secretory responses were evaluated. 2. In the absence of the drugs, the secretion of choline-containing phospholipids over a 1 hr period averaged 3.97% of the total cellular labeled phospholipids. Ebrotidine caused a dose-dependent increase in the rate of phospholipid secretion which was most pronounced at 1 hr and persisted for at least 2 hr. The maximal effect was attained at 120 microM ebrotidine giving a 36% increase in phospholipid secretion. 3. The phospholipid secretory response to ebrotidine was accompanied by an increase in gastric mucosal cell cAMP level which reached a maximum value of 2.1-fold over that of controls at 1 hr. Ranitidine, in contrast, neither evoked increase in cAMP level nor caused any stimulation in phospholipid secretion. 4. The results indicate that the gastroprotective properties of ebrotidine are associated with the ability of the drug to elicit a rapid stimulation in gastric mucus phospholipid secretion, and that ranitidine does not possess such property.

Inhibition of gastric mucosal mucin receptor by Helicobacter pylori lipopolysaccharide: effect of sulglycotide

1. A receptor for mucin was isolated from the solubilized gastric epithelial cell membrane by affinity chromatography on Sepharose-bound wheat germ agglutinin. 2. The receptor protein displayed a molecular weight of 97 kDa and exhibited specific affinity towards mucin-coated surfaces. The optimum for mucin binding occurred at 60-100 micrograms/ml, while the values for the receptor were 2.0-3.1 micrograms/ml. 3. The mucin binding to the receptor was susceptible to Helicobacter pylori lipopolysaccharide which caused maximum inhibition of 91% at 30 mu/ml. This inhibitory effect of the lipopolysaccharide was abolished by a gastroprotective agent, sulglycotide. 4. The effect of sulglycotide was dose dependent and at 50 micrograms/ml produced a 94% restoration in receptor-mucin binding. Furthermore, sulglycotide was also capable of enhancing (97%) the mucin binding to its receptor in the absence of the lipopolysaccharide. 5. The results demonstrate that H. pylori through its lipopolysaccharide interferes in the interaction of mucin with gastric epithelial surfaces and that a gastroprotective agent, sulglycotide, counteracts this effect, and hence is capable of preventing the loss of mucin coat continuity occurring with H. pylori infection.

Gastroprotective agents in mucosal defense against Helicobacter pylori

1. Convincing evidence now exists that infection with H. pylori plays a major role in the pathogenesis of gastric disease. Having a niche bordering two major perimeters of mucosal defenses, the bacterium apparently exerts its detrimental effect on the mucus layer as well as the gastric epithelium. Therefore, gastroprotective agents capable of counteracting these detrimental effects of H. pylori are gaining importance in the treatment of gastric disease. 2. The colonization of gastric mucosa by H. pylori involves specific glycolipid receptors bearing acidic substituents, a process inhibited by gastric sulfomucins. Two antiulcer agents bearing sulfated sugar groups have been demonstrated to possess the ability to interfere with H. pylori colonization process. These are sucralfate and sulglycotide. The two agents are also potent inhibitors of H. pylori glycosulfatase activity directed against indigenous mucosal defenses. 3. A variety of extracellular enzymes such as proteases, lipases and phospholipases, elaborated by H. pylori cause the weakening of the integrity of gastric mucus coat and render the underlying epithelium vulnerable to noxious luminal contents. Among the most potent agents capable of countering the proteolytic activity of H. pylori are nitecapone, ebrotidine and sulglycotide, while ebrotidine and sulglycotide were found to be most effective inhibitors of H. pylori lipolytic activities. 4. The gastric epithelial integrity is compromized by the H. pylori cell-wall lipopolysaccharide untoward effect on the epithelial surface receptors. The interference of the lipopolysaccharide with the laminin receptor was found to be most efficiently countered by ebrotidine, sulglycotide and sucralfate, whereas sulglycotide is the most potent in the reversal of the inhibitory effect of the lipopolysaccharide on mucin receptor binding.

Gastric mucosal EGF and PDGF receptor expression with ulcer healing by ebrotidine

OBJECTIVES

Epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) play important roles in the process of mucosal repair and restitution, and their biological effects are mediated by receptors located on the target cell surfaces. The purpose of this study was to assess the effect of the antiulcer agent, ebrotidine, on the expression of EGF and PDGF receptors with chronic ulcer healing.

METHODS

Chronic gastric ulcers were developed in the rat by acetic acid technique. The animal were divided into two groups and were treated twice daily for 14 consecutive days, either with ebrotidine at 100 mg/kg, or placebo. At different stages of treatment, the animals were sacrificed and used for the isolation and quantification of gastric mucosal EGF and PDGF receptors.

RESULTS

The binding assays revealed that ulcer healing was accompanied by an increase in mucosal expression of both types of receptors. A 1.7-1.8-fold increase in PDGF and EGF receptors occurred by the 4th day after the development of ulcer and reached a maximum of 3-fold increase by the 14th day, when the ulcer was essentially healed. Treatment with ebrotidine caused accelerated ulcer healing (7 days) which was accompanied by a significant enhancement in receptor expression. Compared to the controls, a 1.5-fold increase in EGF and 1.7-fold increase in PDGF receptor expression occurred by the 7th day of ebrotidine treatment, and a 1.4- to 1.5-fold increase was still observed at the 14th day of treatment.

CONCLUSIONS

The results suggest that ebrotidine is capable of enhancement of gastric mucosal proliferative activities associated with ulcer healing through the stimulation of EGF and PDGF receptor expression.

Gastric mucosal laminin receptor expression with ulcer healing by ebrotidine

1. The effect of antiulcer agent, ebrotidine, on the expression of gastric mucosal laminin receptor during ulcer healing was investigated. 2. Rats with acetic acid-induced chronic gastric ulcers were treated twice daily for 14 consecutive days either with ebrotidine at 100 mg/kg or placebo, and then at different stages of treatment used for the isolation and quantitation of gastric mucosal laminin receptor. 3. The binding assays revealed that the ulcer healing was accompanied by an increase in mucosal expression of laminin receptor. A 2.7-fold increase in the receptor expression occurred by 4th day following the development of ulcer and reached a maximum of 8.6-fold increase by the 14th day when the ulcer was essentially healed. 4. Treatment with ebrotidine caused accelerated ulcer healing (7 days), which was accompanied by a remarkable enhancement in the laminin receptor expression. A 2.5-fold increase in the receptor expression over that of controls occurred by the 4th day of ebrotidine treatment, and a 1.7-fold increase was still observed at the 14th day of treatment. 5. The results suggest that ebrotidine, by evoking enhanced mucosal cell laminin receptor expression, promotes reepithelization and, hence, hastens the ulcer healing.

Enhancement in gastric mucosal epidermal growth factor receptor expression by sulglycotide

The effect of intragastric administration of sulglycotide, a cytoprotective sulfated glycopeptide, on the expression of gastric mucosal epidermal growth factor receptor was investigated. The experiments were conducted with groups of rats, one receiving twice daily for 5 consecutive days a dose of 200mg/kg sulglycotide, and the other only vehicle. Mucosal cell membranes were isolated from the stomachs at 16, 40 and 88h after the last dose, and used for EGF receptor assays. The binding assays revealed a marked increase in mucosal EGF receptor expression with sulglycotide. Compared to the controls, the sulglycotide-treated group showed a 4-fold increase in the EGF receptor expression at 16h after the last dose of sulglycotide, a 4.7-fold increase in the EGF receptor was observed by the 40h, and a 4.2-fold increase was still evident at 88h following the treatment. The results demonstrate that sulglycotide exhibits remarkable ability to enhance the gastric mucosal expression of EGF receptor.

Association of salivary bacterial aggregating activity with sulfomucin

The requirements of human salivary mucins for aggregating potential towards the common cariogenic oral bacteria, S. mutans and S. sanguis, were investigated. Agglutination inhibition assays demonstrated that the aggregating capacity towards bacteria resides in the acidic mucin fraction. The inhibitory activity of the acidic mucin decreased only 2-4-fold following removal of sialic acid, whereas the desulfation caused a complete loss of the inhibitory potential against both bacteria. Furthermore, the aggregating capacity of mucin-derived sulfated oligosaccharide was found to be 16-fold higher than that of the sialic acid containing oligosaccharide. The results point towards the importance of salivary sulfomucins as a predominant factor in the defense of oral cavity against cariogenic bacteria.

Activation of arachidonoyl phospholipase A2 in prostaglandin-mediated action of sucralfate

1. The mechanism of sucralfate-induced gastric mucosal prostaglandin generation was investigated using mucosal cells labeled with [14C]choline and [3H]arachidonic acid. 2. In comparison to the controls, the cells maintained in the presence of sucralfate showed a concentration dependent increase in lysophosphatidylcholine (LPC) synthesis and PGE2 generation. The maximal effect was attained at 25 microM sucralfate giving a 45.7% increase in LPC and 70% increase in PGE2. 3. Pretreatment with indomethacin prior to sucralfate, while causing inhibition in PGE2 generation, had no effect on LPC production and led to accumulation of free arachidonic acid. In the case of pretreatment with NDGA, the sucralfate caused increased LPC synthesis accompanied by enhanced PGE2 generation without free arachidonic acid accumulation. 4. The stimulatory effect of sucralfate on LPC synthesis and PGE2 generation was inhibited by phospholipase A2 inhibitors, mepacrine and BPB. The inhibitory effect was concentration dependent and attained maximum at 40 microM for BPB and 80 microM for mepacrine. 5. The results for the first time demonstrate that the enhancement in gastric mucosal prostaglandin generation by sucralfate results from the stimulation of mucosal phospholipase A2 for arachidonic acid release.

Regulation of gastric mucosal calcium channel activity by an antiulcer agent, ebrotidine

Ebrotidine is a new H2-receptor antagonist also known for its gastroprotective effect against ethanol-induced mucosal injury. In this study, we investigated the effect of ebrotidine on the activity of the gastric mucosal calcium channels. The channel complex was isolated from the solubilized gastric epithelial cell membranes by affinity chromatography on wheat germ agglutinin. The complex following labeling with [3H] PN200-110 was reconstituted into phosphatidylcholine vesicles which exhibited active 45Ca2+ uptake into intravesicular space and responded in a concentration-dependent manner to calcium channel activator, BAY K8644, as well as to calcium channel antagonist, PN200-100. The 45Ca2+ uptake was inhibited by ebrotidine which caused maximum inhibitory effect of 54.9% at 50 micrograms/ml. The gastric mucosal calcium channels on epidermal growth factor binding (EGF) in the presence of ATP responded by an increase in tyrosine phosphorylation of 55 and 170 kDa proteins, and the vesicles containing the phosphorylated channels displayed a 48% greater 45Ca2+ uptake. This phosphorylation process was inhibited by ebrotidine which also interfered with the binding of EGF to calcium channel protein. The results point towards the importance of EGF in the maintenance of gastric mucosal calcium homeostasis, and suggest that ebrotidine has the ability to protect the cellular integrity from calcium imbalance by modulating the EGF-stimulated gastic mucosal calcium channel phosphorylation.

Sulglycotide effect on the proteolytic and lipolytic activities of Helicobacter pylori toward gastric mucus

OBJECTIVES

Infection with Helicobacter pylori is now recognized as a major factor in the etiology of gastric disease, and among the detrimental effects this bacterium exerts on the mucosal integrity is the elaboration of extracellular protease and lipase enzymes capable of mucus protein and lipids degradation. We present here evidence that the activities of these enzymes are inhibited by an gastroprotective agent, sulglycotide.

METHODS

The grown colonies of bacterium were washed with saline, filtered through sterilization filter, and the filtrate used as the enzyme source.

RESULTS

In the absence of sulglycotide, the H. pylori protease caused extensive degradation of human gastric mucus, while free fatty acids, glycerol monooleate and lysophosphatidylcholine were produced by the action of H. pylori lipase and phospholipase A enzymes. Introduction of sulglycotide to the incubation systems led to the reduction in the rate of mucus protein and lipid degradation. The rate of proteolysis inhibition was proportional to sulglycotide concentration up to 45 micrograms/ml, at which point a 43% reduction in mucus degradation was attained, whereas the maximum inhibition of lipase (39%) and phospholipase A (98%) activities occurred at a sulglycotide concentration of 100 micrograms/ml.

CONCLUSIONS

This study indicates that sulglycotide is capable of counteracting the mucolytic activity of H. pylori, and thus may be of value in the therapy of H. pylori-associated gastric diseases.

Inhibition of gastric mucosal mucin receptor by Helicobacter pylori lipopolysaccharide

A gastric mucosal mucin receptor has been isolated from the epithelial cell membrane by affinity chromatography on wheat germ agglutinin. The receptor protein displayed an apparent molecular weight of 97kDa and exhibited binding specific to gastric mucin in a concentration-dependent manner. The binding of mucin to the mucosal receptor was inhibited by lipopolysaccharide from H. pylori. The inhibitory effect was proportional to the concentration of lipopolysaccharide up to 30 micrograms/ml, at which concentration a 91% decrease in binding occurred. The results suggest that H. pylori lipopolysaccharide is capable of disrupting the integrity of mucus perimeter of gastric mucosal defense by interfering with epithelial cell-mucin binding.

Identification of buccal mucosal mucin receptor

A receptor for salivary mucin was isolated from epithelial cell membrane of buccal mucosa by a procedure involving membrane solubilization with octylglucoside followed by affinity chromatography on Sepharose-bound wheat germ agglutinin. The receptor protein displayed an apparent molecular weight of 97kDa and exhibited binding specific to mucin in a concentration-dependent manner. The receptor, furthermore, showed a requirement for carbohydrate chains in mucin for binding, as their removal caused a marked (89%) reduction in binding capacity. Scatchard analysis revealed a linear plot with a single class of high affinity binding (Kd = 1.1 microM; Bmax = 7.68nmol/mg protein. The results provide for the first time evidence for the existence in buccal mucosa of a specific receptor for salivary mucin.

Characterization of gastric mucosal mucin receptor

Mucin receptor was isolated from gastric epithelial cell membrane by a procedure involving membrane solubilization with octylglucoside followed by affinity chromatography on Sepharose-bound wheat germ agglutinin. The receptor protein yielded on SDS-PAGE a single 97kDa band and displayed specific affinity, in a concentration-dependent manner, towards the mucin-coated surface. The receptor showed requirement for carbohydrate chains in mucin for binding, as their removal caused a marked (87%) reduction in binding capacity. Scatchard analysis revealed a linear plot with a single class of high affinity binding (Kd = 43.8 nM; Bmax = 140 pmol/mg protein) sites. The results demonstrate for the first time the presence in gastric mucosa of a specific receptor for mucin.

Helicobacter pylori lipopolysaccharide inhibition of gastric mucosal laminin receptor: effect of sulglycotide

1. The effect of cell-wall lipopolysaccharide from Helicobacter pylori, a bacterium implicated in the etiology of gastric disease, on the gastric mucosal laminin-receptor was investigated. 2. The receptor, isolated from gastric epithelial cell membrane by affinity chromatography on laminin-coupled Sepharose, was radioiodinated and incorporated into liposomes which exhibited specific affinity towards laminin-coated surface. 3. The binding of liposomal receptor to laminin-coated surface was inhibited by H. pylori lipopolysaccharide, which at 50 micrograms/ml caused a nearly complete (97%) inhibition in binding. 4. The inhibitory effect of the lipopolysaccharide was prevented by a cytoprotective agent, sulglycotide, that evoked a 92% restoration in binding at 40 micrograms/ml. 5. The results demonstrate that through its lipopolysaccharide H. pylori is capable of disrupting the gastric mucosal integrity and that this detrimental effect could be successfully countered by sulglycotide.

Inhibition of Helicobacter pylori glycosulfatase activity towards human gastric sulfomucin by a gastroprotective agent, sulglycotide

1. A glycosulfatase activity towards human gastric sulfomucin was identified in the extracellular material elaborated by Helicobacter pylori, a pathogen implicated in the etiology of gastric disease. 2. The purified enzyme displayed an apparent molecular weight of 30 kDa, and exhibited maximum activity at pH 5.7 in the presence of 0.3% Triton X-100 and 100 mM CaCl2. 3. The H. pylori glycosulfatase activity towards human gastric sulfomucin was inhibited by a gastroprotective agent, sulglycotide. The inhibitory effect was proportional to the concentration of sulglycotide up to 20 micrograms/ml, at which a 98% decrease in mucin desulfation occurred. However, the drug lost the inhibitory effect following its chemical desulfation. 4. The results demonstrate that sulglycotide is a potent inhibitor of H. pylori glycosulfatase and, hence, may be of value in the treatment of gastric disease associated with this bacterial infection.

Enhancement in gastric mucosal laminin receptor expression with ulcer healing

The expression of gastric mucosal laminin receptor with chronic ulcer healing was investigated. The receptor protein was isolated from gastric epithelial cell membrane of rats at various stages of ulcer healing and following radioiodination incorporated into vesicles which exhibited specific affinity towards laminin-coated surface. The binding assays revealed that the ulcer healing was accompanied by an increase in laminin receptor expression. A significant increase (2.5-fold) in the receptor expression occurred by the third day following the development of ulcer, reached a maximum of 8.6-fold increase by the 14th day when the ulcer was virtually healed, and its high level remained for at least 20 days. The results demonstrate the importance of laminin receptor as an indice of gastric mucosal repair in ulcer healing.

Regulation of buccal mucosal calcium channel activity by salivary mucins

1. The effect salivary mucins on the activity of calcium channel isolated from buccal mucosal cell membranes was investigated. The uptake of 45Ca2+ while only moderately (15%) affected by the intact low and high molecular weight mucin forms, was significantly inhibited, by the acidic low and high molecular weight salivary mucins which evoked 64 and 60% inhibition, respectively. 2. The inhibitory effect of salivary mucins was associated with the sialic acid and sulfate ester groups of the carbohydrate chains, as the removal of either group caused partial loss in the glycoproteins inhibition, and the complete loss in the inhibitory effect occurred following desialylation and desulfation. 3. The channel in the presence of epidermal growth factor (EGF) and ATP responded by an increase in tyrosine phosphorylation of 55 and 170 kDa proteins, and the phosphorylated channels showed a 46% increase in 45Ca2+ uptake. The phosphorylation and the calcium uptake were susceptible to inhibition by a specific tyrosine kinase inhibitor, genistein. 4. The binding of EGF to calcium channel receptor protein was inhibited by the low and high molecular weight acidic mucins, causing 41.2 and 36.1% reduction, respectively. This reduction in binding was dependent upon the presence of sulfate ester and sialic acid groups, as evidenced by the loss of the glycoproteins' inhibitory capacity following removal of these groups. 5. The results for the first time demonstrate that salivary mucins actively participate in the modulation of the EGF-controlled buccal mucosal calcium channel activity expression, a process of importance to the preservation of oral tissue integrity.

Effect of ebrotidine on gastric mucosal EGF and PDGF receptor expression

The effect of ebrotidine, a new H2-blocker with gastroprotective properties, on the expression of gastric mucosal epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) receptors, was investigated. Mucosal cell membranes were isolated from rats receiving twice daily for 5 days a dose of 100mg/kg ebrotidine or 100mg/kg ranitidine or vehicle only. Assays for EGF and PDGF revealed the presence of both types of receptors, activation of which led to enhanced tyrosine kinase activity. The receptor binding values in the control group were 2.4 fmol for EGF and 1.45 fmol/mg protein for PDGF, whereas the values in the ebrotidine group increased for EGF by 65.7% and 38.6% for PDGF, but no such effect was observed with ranitidine. The results suggest that the gastroprotective properties of ebrotidine stem from its ability to stimulate the epithelial proliferative activities through the enhancement of EGF and PDGF receptors expression.

Salivary and plasma insulin levels in man

Changes in plasma and salivary immunoreactive insulin were studied in saliva and blood of 9 healthy subjects following either oral glucose or a test meal ingestion at 30 min intervals for up to 3h. The levels of plasma immunoreactive insulin reached maximum at 60 min with a value of 62.77 +/- 6.52 microU/ml after the glucose load and 62.62 +/- 6.52 microU/ml after the test meal. In the case of salivary immunoreactive insulin levels, the maximum was attained at 90 min with a value of 18.47 +/- 2.68 microU/min after the glucose load and 22.40 +/- 2.01 microU/min after the test meal. Positive linear correlation (r = 0.74) was found between the salivary and plasma immunoreactive insulin levels.

Differential expression of salivary mucin bacterial aggregating activity with caries status

1. The low and high mol. wt mucin forms were isolated from saliva of caries-resistant (CR) and caries-susceptible (CS) individuals, and assessed for their bacterial aggregating potential towards S. mutans and S. sanguis, the common cariogenic microorganisms encountered in the oral cavity. 2. The high mol. wt mucin from both groups of subjects exhibited similar protein and carbohydrate content, but the level of covalently bound fatty acids was significantly lower in the CR group. The mucin from CR group showed only a weak inhibitory potential, and no inhibitory activity was observed with the mucin of CS group. 3. The low mol. wt mucins from both groups, while displaying compositional similarities, showed a marked variation in the bacterial aggregating activity. With both bacteria, the activity of the mucin from CR group was at least 128-fold greater than that of CS group. 4. The conversion of the high mol. wt mucin to a low mol. wt form through the action of salivary protease produced in both groups enhancement in mucin's bacterial aggregating capacity. This enhancement was, however, considerably less pronounced in the case of mucin from CS group. 5. The results for the first time demonstrate that the bacterial aggregating epitope of salivary mucins is expressed to a greater extent in CR individuals, and that this epitope is apparently more accessible to bacteria in the low mol. wt mucin form.

Modulation of gastric mucosal calcium channel activity by mucus glycoprotein

1. The effect of gastric mucus glycoprotein on the activity of calcium channel isolated from gastric epithelial cell membrane was investigated. The 45Ca2+ uptake into the vesicle-reconstituted channels, while only moderately (14%) affected by the intact mucus glycoprotein, was found significantly inhibited (59%) by the acidic glycoprotein fraction. This effect was associated with the sialic acid and sulfate ester groups of the glycoprotein, as their removal caused a loss in the inhibition. 2. The channel complex in the presence of epidermal growth factor (EGF) and ATP responded by an increase in protein tyrosine phosphorylation of 55 and 170 kDa proteins, and the vesicles containing the phosphorylated channels showed a 50% increase in 45Ca2+ uptake. The phosphorylation and the calcium uptake were susceptible to inhibition by a specific tyrosine kinase inhibitor, genistein. 3. The channel protein phosphorylation was inhibited by the acidic mucus glycoprotein, which also interfered with the binding of EGF to the channel protein. The inhibitory effect was dependent upon the presence of sulfate ester and sialic acid groups, as evidenced by the loss of the glycoprotein inhibitory capacity following their removal. 4. The results suggest that the acidic gastric mucus glycoproteins, by modulating the EGF-controlled calcium channel phosphorylation, play a major role in gastric mucosal calcium homeostasis.

[Evaluation of microsomal enzyme function in the liver in patients with duodenal ulcer treated with famotidine]

The studies of microsomal liver enzyme activity by means of a respiratory test with 14C-aminopyrine (ABT) were carried out in 20 patients with duodenal ulcer treated for eight weeks with famotidine. The respiratory test was performed before the introduction of treatment (group I), after four weeks of treatment (group II), and after eight weeks of treatment (group III). The mean value of the respiratory test before treatment was 5.32% of the dose/h. After four weeks of treatment with famotidine a significant decrease was found of the test value (x = 4.79% of the dose/h). An even stronger inhibitory action of famotidine on the microsomal system was shown after eight weeks of the treatment (x = 4.46% of the dose/h). These results evidence a depressive effect of famotidine on the activity of liver monooxygenases. In patients taking this drug, other drugs metabolised in the hepatocyte microsomal system should be used with high caution, as well as those which are known to be inhibitors of this system.

Control of mucin molecular forms expression by salivary protease: differences with caries

1. A protease activity capable of degradation of the high mol. wt salivary mucus glycoprotein to a low mol. wt glycoprotein form was identified in human submandibular gland secretion. 2. The protease exhibited optimum activity at pH 7.0-7.4, and gave on SDS-PAGE under reducing conditions two major protein bands of 48 and 53 kDa. The enzyme showed susceptibility to PMSF, alpha 1antitrypsin, and egg white and soybean inhibitors, a characteristic typical to serine proteases. 3. The activity of the protease towards the high mol. wt mucus glycoprotein was found to be 3.8-fold higher in submandibular gland secretion of caries-resistant individuals than that of caries-susceptible. Furthermore, the enzyme from both groups displayed greater activity against the mucus glycoprotein of caries-resistant subjects. 4. Since the low mol. wt salivary mucus glycoprotein form is more efficient in bacterial clearance than the high mol. wt mucin, the enhanced expression of this indigenous salivary protease activity towards mucin may be the determining factor in the resistance to caries.

[Transforming growth factors and their role in chronic liver diseases]

The transforming growth factors are endogenous polypeptide substances having own cell receptors. Among them two main factors have been isolated--transforming growth factor alpha (TGF alpha) and beta (TGF beta). TGF alpha is secreted by activated proliferating hepatocytes and by certain neoplastic cells. It stimulates the synthesis of DNA and migration of hepatic epithelial cells. In chronic liver diseases it is produced in increased amounts and stimulates then proliferation and regeneration. TGF beta is released by non-parenchymal liver cells, thrombocytes, and neoplastic cells. It inhibits the synthesis of DNA in many cells, inhibits the synthesis of albumins and fibrinogen and regulates the production of acute phase proteins. In chronic liver diseases it increases the production of fibronectin and collagen, inhibiting at the same time their enzymatic breakdown. TGF beta participates in the development and progression of hepatic fibrosis.