Layers Of Rat Gastric Mucosa Research Articles

The mucin biosynthesis stimulated by epidermal growth factor occurs in surface mucus cells, but not in gland mucus cells, of rat stomach

Although epidermal growth factor (EGF) accelerates gastric mucin biosynthesis, information on whether its activation is limited to the specific mucus-producing cells is lacking. In this paper, we investigated the effects of EGF on mucin biosynthesis and the expression of its receptor in distinct layers of rat gastric mucosa, including the possible participation of nitric oxide (NO). EGF enhanced the incorporation of [ 3H]glucosamine and [ 14C]threonine into the mucin in the full-thickness tissues of the gastric mucosa. This stimulation disappeared on the removal treatment of the surface mucosal layer chiefly consisting of surface mucus cells. The EGF-induced increase in [ 3H]-labeled mucin in the full-thickness mucosa was not suppressed by either N G-nitro- l-arginine (10 −5 M) or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (10 −5 M). The EGF-receptor-mRNA expression was high in the surface mucosal layer but low in the deep and muscle layers of the stomach. These results suggest that EGF-induced stimulation of mucin biosynthesis is limited to the surface mucus cells of the rat gastric mucosa and is independent of the NO pathway.

Hepatocyte growth factor region specifically activates mucin synthesis in rat stomach

We investigated the effects of hepatocyte growth factor (HGF) on mucin biosynthesis and the expression of its receptor in distinct sites and layers of rat gastric mucosa. HGF stimulated the mucin biosynthesis in the surface and gland mucus cells of corpus, but not in the antrum, without its trophic effects. The HGF-receptor mRNA expression was high in the surface and deep corpus mucosa, but low in the antrum. These results demonstrate that HGF has distinct effects on mucin biosynthesis in a specific region of rat stomach, suggesting different regulatory mechanisms underlying the mucus metabolism of distinct mucus-producing cells.

Lafutidine-induced stimulation of mucin biosynthesis mediated by nitric oxide is limited to the surface mucous cells of rat gastric oxyntic mucosa

Although the new histamine H 2 receptor antagonist, lafutidine (FRG-8813), N-[4-[4-(piperidinylmetriyl)pyridyl-2-oxy]-(Z)-2-butenyl]-2-(furfurylsulfinyl)acetamide accelerates mucin metabolism of rat gastric mucosa, the physiological mechanisms by which this drug stimulates the biosynthesis remain unclear. In this paper, we report the effect of lafutidine on mucin biosynthesis in distinct sites and layers of rat gastric mucosa, including the possible participation of nitric oxide (NO). Lafutidine enhanced [ 3H]glucosamine incorporation into the mucin in the full thickness corpus mucosa, but not in the antrum. This stimulation on mucin biosynthesis disappeared by the removal treatment of surface mucosal cells. The lafutidine-induced increase of [ 3H]-labeled mucin in the corpus was completely blocked by either N G-nitro-L-arginine (10 −5M) or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazolme-l-oxyl-3-oxide (10 −5M), The inhibitory action of N G-nitro-L-arginine was totally reversed by L-arginine (5 x 10-3 M). These results suggest that the lafutidine-induced stimulation of mucin biosynthesis mediated by NO is limited to the surface mucous cells of rat gastric oxyntic mucosa.

Distinct effects of tetragastrin, histamine, and CCh on rat gastric mucin synthesis and contribution of NO.

Although gastrin, histamine, and carbachol (CCh) accelerate gastric mucin metabolism, information about their target cells of mucin production is lacking. To clarify this, we examined the effects of these stimulants, including the possible participation of nitric oxide (NO), on mucin biosynthesis in distinct sites and layers of rat gastric mucosa. Pieces of tissue obtained from the corpus and antrum were incubated in a medium containing radioactive precursors and each stimulant, with or without NO synthase (NOS) inhibitor. Distribution of NOS was compared with that of the specific mucins by immunostaining using specific antiserum and monoclonal antibodies. In the full-thickness corpus mucosa, tetragastrin enhanced [3H]glucosamine incorporation into mucin but had no effect on [14C]threonine incorporation. Both histamine and CCh dose dependently increased 3H- and 14C-labeled corpus mucin. Only CCh stimulated antral mucin biosynthesis. CCh stimulation was noted in the corpus mucosa after removal of surface mucous cells, but stimulation by tetragastrin or histamine disappeared as a result of this pretreatment. Only tetragastrin-induced activation was completely blocked by the NOS inhibitor. NOS immunoreactivity was limited to surface mucous cells. Mucus-producing cells present in the different sites and layers of the gastric mucosa have distinct mechanisms for regulation of mucin biosynthesis. Gastrin-stimulated mucin biosynthesis mediated by NO is limited to surface mucous cells of rat gastric oxyntic mucosa.

Recovery of mucin content in surface layer of rat gastric mucosa after HCl-aspirin-induced mucosal damage.

Quantitative changes in mucin (mucus glycoprotein) in different layers of rat gastric mucosa after mucosal damage induced by acidified acetylsalicylic acid (HCl-aspirin; 0.15N HCl, 20-200 mg acetylsalicylic acid/kg body weight) were studied. More than 50 mg/kg HCl-aspirin led to a significant increase in macroscopic gastric injury (expressed as ulcer index) at 3 h, compared with control (no aspirin) and there was a significant recovery at 7 h. Three h after dosing with 50 mg/kg acidified aspirin, there was superficial mucosal damage and decreased mucin content in the surface mucosal layer. Mucin production recovered 7 h after the administration of 50 mg/kg acidified aspirin. Doses of acidified aspirin higher than 100 mg/kg decreased mucin content in the surface and deep corpus mucosal layers and no recovery was seen 7 h after the administration. Physiological damage after the administration of 50 mg/kg HCl-aspirin was limited mainly to surface epithelial mucus cells. An experimental model in which superficial erosion was induced in rat gastric mucosa was established with low-dose HCl-aspirin.

Stimulation of mucin metabolism in rat gastric mucosa by histamine.

We examined the effects of histamine on mucin localized in the different regions and layers of rat gastric mucosa by determining the changes in the content as well as the biosynthetic activity of the mucin. In vivo administration of 0.8 mg/kg of histamine, which could not induce a concomitant gastric acid secretion, caused a significant increase in the mucin content in the corpus mucosa, but not in the antral mucosa. This increase was due to a significant accumulation of the mucin in the mucus gel and surface mucosa of the corpus region, whereas that in the deep mucosa did not significantly change. In the in vitro incubation system of rat gastric mucosa, histamine and dibutyryl cyclic AMP significantly increased [3H]-labeled mucin in the corpus. The histamine-induced acceleration of mucin biosynthesis was suppressed by ranitidine, but not pyrilamine. In the antrum, the biosynthetic activity showed no significant change by histamine. These results suggest that histamine promotes mucin metabolism via histamine H2 receptors in the surface mucosal layer of the corpus.

Establishment of monoclonal antibodies against carbohydrate moiety of gastric mucins distributed in the different sites and layers of rat gastric mucosa

Eight monoclonal antibodies (MAbs), designated RGM21 approximately RGM42, were generated against mucin purified from the rat gastric mucosa. By applying ELISA, all of these MAbs were proved to react not only with the purified mucin, but also with the oligosaccharide mixture obtained from the antigenic mucin by alkaline borohydride treatment. Treatment of the mucin-attached ELISA well with trypsin, sodium periodate or galactose oxidase prior to the addition of the MAb was applied to characterize these MAbs. Histochemical observation indicated that all these MAbs were able to stain the formalin fixed-paraffin embedded sections of the rat gastroduodenal mucosa. Although each of these MAbs reacted with distinct mucus-producing cells localized in particular regions of the gastroduodenal mucosa, their staining specificity could generally be classified into four groups. These MAbs might be useful for estimating the physiological and pathological changes of mucins in the gastric mucosa.

Effects of traditional herbal medicine on gastric mucin against ethanol-induced gastric injury in rats

The effect of the traditional herbal medicine, Rikkunshi-to and its component crude drugs, Zingiberis Rhizoma and Glycyrrhizae Radix, on the gastric mucin was studied using a method developed to separate and quantify the mucin localized in the different layers of rat gastric mucosa. The oral administration of spray-dried extract to Rikkunshi-to (1000 mg/kg), Zingiberis Rhizoma (500 mg/kg) and Glycyrrhizae Radix (500 mg/kg) significantly prevented gastric mucosal damage induced by 70% ethanol in rats. In ethanol-treated rats the mucin content of the deep mucosa was reduced, and the reduction of the deep corpus mucin content was significantly inhibited by pretreatment of Rikkunshi-to and Zingiberis Rhizoma. Rikkunshi-to and Glycyrrhizae Radix pretreatment increased the surface mucin content by 140 and 146%, respectively. The effect on the gastric mucin by each drug differed in the different layers of the gastric mucosa.

Comparison of the mucus glycoproteins present in the different layers of rat gastric mucosa

1. 1. Applying a newly developed separation method, mucus glycoproteins (mucins) present in the different layers of gastric mucosa in rats were studied. 2. 2. Distributions of mucin in the four layers of gastric mucosa expressed as mg mucin hexose per animal are: deep mucosa of corpus, 705; deep mucosa of antrum, 163; surface mucus, 421; mucus gel, 30; and soluble mucus, 173. 3. 3. Relatively low molecular sugar chains, having a small amount of neutral sugars, are rich in the deep corpus and deep antral mucin. 4. 4. Higher molecular size carbohydrate chains, rich in fucose and galactose, are abundant in the surface mucus and mucus gel-derived mucin.

Effects of tetragastrin on mucus glycoprotein in rat gastric mucosal protection.

The effects of tetragastrin on mucus glycoprotein (mucin) metabolism and mucosal protection in rat gastric mucosa were investigated. Rats were administered with various doses of tetragastrin (12, 120, or 400 micrograms/kg body weight; s.c.), followed by 50% ethanol-induced gastric injury. Tetragastrin caused a significant increase in mucin content in the corpus mucosa and prevented 50% ethanol-induced gastric mucosal damage in a dose-dependent manner. For assessment of the effects of tetragastrin on the metabolism of gastric mucin in detail, changes in mucin distribution in the three different layers of rat gastric mucosa were examined one hour after single administration of tetragastrin. A significant increase in the mucin content was noted in the mucus gel and surface mucosal layer. Mucin content in the deep mucosa corresponding mainly to the mucus neck cell mucin underwent virtually no change by this treatment. An increase in mucin in the mucus gel and surface mucosa would thus appear due to the administration of tetragastrin and may possibly be related to the protective action of the gastric mucosa against injury. The data demonstrate a possibility that gastrin may have potential for enhancing gastric mucosal protection associated with mucus secretion and/or mucus synthesis on the surface mucosa of rat gastric mucosa.

A separating method for quantifying mucus glycoprotein localized in the different layer of rat gastric mucosa.

A method was devised for separating rat gastric mucosa into three layers each containing a different mucin species. The mucus gel (first layer) was removed by stirring the gastric mucosa in a solution of phosphate-buffered saline containing 2% N-acetylcysteine. The surface mucosa (second layer), rich in surface mucus cells, was then separated from the deep mucosa (third layer) containing mucus neck cells, by scraping with forceps. The effectiveness of this method was confirmed by light microscopical observation after GOCTS-PCS (dual staining by the galactose oxidase-cold thionin Schiff method and paradoxical concanavalin A method) and AB-PAS staining (dual staining with alcian blue and the periodic acid Schiff method). The fixed specimen of scraped mucus and cell debris was rich in AB-PAS and GOCTS positive mucus, but was hardly stained by PCS, indicating mucus derived from surface mucus cells to have been efficiently recovered from this preparation. The residual mucosa could be stained by PCS but hardly at all by AB-PAS or GOCTS. The lyophilized powder specimens obtained from the three different layers of rat gastric mucosa were used to extract and quantify mucus glycoprotein (mucin). This was done to examine changes in mucin content in the three layers of gastric mucosa one hour following the oral administration of 20% ethanol or 0.35 N hydrochloric acid, both mild irritants. Mucin content was noted to significantly increase in the first layer but hardly at all in the second layer. In the third layer, it decreased significantly by 0.35 N hydrochloric acid, but changed only slightly by 20% ethanol administration.(ABSTRACT TRUNCATED AT 250 WORDS)