Normal Rat Gastric Mucosa Research Articles

O32 Curcumin induces expression of 15-hydroxyprostaglandin dehydrogenase in normal gastric mucosa RGM-1 cells and mouse stomach in vivo: A potential role of AP-1

Overproduction of prostaglandin E 2 (PGE 2 ) has been reported to be implicated in carcinogenesis. The intracellular level of PGE 2 is regulated not only by its biosynthesis, but also by the degradation process. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is the key enzyme that catalyzes the inactivation of PGE 2 . In the present study, we found that curcumin, a yellow coloring agent present in the rhizome of Curcuma longa Linn (Zingiberaceae), induced expression of 15-PGDH at both the protein and mRNA levels in normal rat gastric mucosa cells (RGM-1). By using deletion constructs of the 15-PGDH promoter, we have found that activator protein-1 (AP-1) is the most essential transcription factor responsible for curcumin-induced upregulation of 15-PGDH expression. In addition, oral administration of curcumin increased the expression of 15-PGDH in the mouse stomach. Curcumin enhanced the expression of c-Jun and c-Fos in the nuclear fraction of RGM-1 cells and the mouse stomach in vivo . Knockdown of c- jun , a gene encoding one of the major components of AP-1, suppressed curcumin-induced expression of 15-PGDH. In addition, curcumin increased phosphorylation of ERK1/2 and JNK. Curcumin-induced 15-PGDH expression was abrogated by the pharmacological inhibition of the aforementioned kinases. In contrast, tetrahydrocurcumin which lacks the α , β -unsaturated carbonyl group failed to induce expression of 15-PGDH, suggesting that the electrophilic α , β -unsaturated carbonyl group of curcumin is essential for its induction of 15-PGDH expression in RGM-1 cells. Taken together, our study suggests that curcumin-induced upregulation of 15-PGDH in RGM-1 cells and mouse stomach through activation of AP-1 may contribute to chemopreventive effects of this phytochemical on inflammation-associated gastric carcinogenesis.

Effect of the IGF-1/PTEN/Akt/FoxO signaling pathway on the development and healing of water immersion and restraint stress-induced gastric ulcers in rats

Insulin-like growth factor 1 (IGF-1) and Akt [also known as protein kinase B (PKB)] proteins have been reported to exhibit gastroprotective effects by reducing water immersion and restraint stress (WRS)-induced gastric mucosal cellular apoptosis. To confirm whether the IGF-1/PTEN/Akt/FoxO signaling pathway is effective in protecting against gastric ulcers, our current study was conducted to examine the expression and localization of IGF-1, phosphatase and tensin homologue deleted on chromosome 10 (PTEN), Akt and O subfamily of forkhead box (FoxO) proteins, caspase-3 activity and the number of apoptotic cells in gastric mucosa of rats subjected to WRS. Our results demonstrated that WRS induced gastric ulcers by enhancing cell apoptosis in rat gastric mucosa. In addition, in normal rat gastric mucosa, PTEN, total Akt and FoxO1 were found mainly in the cell cytoplasm of fundic glands in the lamina propria close to the muscularis mucosa. In addition, strong staining of IGF-1, FoxO3a and FoxO4 in the gastric mucosa was primarily concentrated in the cell cytoplasm of the fundic glands in whole lamina propria. However, in rat gastric ulcers, IGF-1, total Akt, FoxO3a and FoxO4 were localized in proximity to the base of the ulcer margin and were also present in the granulation tissues of the gastric ulcers. Moreover, in the rat gastric ulcers, the mRNA transcript levels of IGF-1, PTEN, Akt-1, Akt-2, FoxO3 and FoxO4 were upregulated in the gastric ulcer margin, with a peak between Days 4 and 8 following 7 h of WRS. In conclusion, our results imply that the IGF-1/PTEN/Akt/FoxO signaling pathway plays a certain role(s) in the protection against ulceration through the regulation of cellular apoptosis as observed in the development and healing of rat gastric ulcers.

Abstract 1625: Curcumin induces expression of 15-hydroxyprostaglandin dehydrogenase in normal gastric mucosa RGM-1 cells: Possible involvement of AP-1

Abstract Overproduction of prostaglandin E2 (PGE2) has been reported to be implicated in carcinogenesis. The intracellular level of PGE2 is regulated not only by its biosynthesis, but also by the degradation process. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is the key enzyme that catalyzes the first step in the inactivation of PGE2. In the present study, we found that curcumin, a yellow coloring agent present in the rhizome of Curcuma longa Linn (Zingiberaceae), induced expression of 15-PGDH in normal rat gastric mucosa cells (RGM-1) in a concentration and time dependent manners. The mRNA level of 15-PGDH was also increased by curcumin treatment. By using deletion constructs of 15-PGDH promoter, we found that activator protein-1 (AP-1) is the most essential transcription factor responsible for curcumin-induced upregulation of 15-PGDH expression. Curcumin induced phosphorylation of ERK1/2 and JNK1/2, but did not affect activation of p38 MAP kinase. However, treatment with U0126 and SP600125, pharmacological inhibitors of ERK and JNK, respectively failed to suppress the induction of 15-PGDH expression in curcumin-treated RGM-1 cells. Curcumin enhanced the expression of c-Jun, c-Fos and CREB in the nuclear fraction of RGM-1 cells. In contrast, tetrahydrocurcumin which lacks the α,β-unsaturated carbonyl group failed to induce expression 15-PGDH, suggesting that the electrophilic α,β-unsaturated carbonyl group of curcumin plays a critical role in its induction of 15-PGDH expression in RGM-1 cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1625. doi:1538-7445.AM2012-1625

Abstract B68: Curcumin-induced expression of 15-hydroxyprostaglandin dehydrogenase in normal gastric mucosa RGM-1 cells: Possible involvement of AP-1

Abstract Overproduction of prostaglandin E2 (PGE2) has been reported to be implicated in carcinogenesis. The intracellular level of PGE2 is regulated not only by its biosynthesis, but also by the degradation process. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is the key enzyme that catalyzes the first step in the inactivation of PGE2. In the present study, we have found that curcumin, a yellow colouring agent present in the rhizome of Curcuma longa Linn (Zingiberaceae), induced expression of 15-PGDH in normal rat gastric mucosa cells (RGM-1) in a concentration and time dependent manner. The mRNA level of 15-PGDH was also increased by curcumin treatment. By using deletion constructs of 15-PGDH promoter, we found that activator protein-1 (AP-1) is the most essential transcription factor responsible for curcumin-induced upregulation of 15-PGDH expression. Curcumin induced phosphorylation of ERK1/2 and JNK1/2, but did not affect activation of p38 MAP kinase. However, treatment with U0126 and SP600125, pharmacological inhibitors of ERK and JNK, respectively failed to suppress the induction of 15-PGDH expression in curcumin-treated RGM-1 cells. Curcumin enhanced the expression of c-Jun, c-fos and CREB in the nuclear fraction of RGM-1 cells. In contrast, tetrahydrocurcumin which lacks the α,β-unsaturated carbonyl group failed to induce expression 15-PGDH, suggesting that the electrophilic α,β-unsaturated carbonyl group of curcumin plays a critical role in its induction of 15-PGDH expression in RGM-1 cells. These results suggest that curcumin-induced expression of 15-PGDH may be mediated by activation of AP-1 transcription factor. Citation Information: Cancer Prev Res 2011;4(10 Suppl):B68.

Effect of Glyceric Acid Calcium Salt on the Viability of Ethanol-Dosed Gastric Cells

D-Glyceric acid (D-GA) calcium has been reported to accelerate ethanol oxidation in vivo in rats (Eriksson et al., Metabolism, 56, 895-898 (2007)). However, no other reports have shown that D-GA can reduce the harmful effects of ethanol. In this study, the effects of D-, L-, and DL-GA calcium on ethanol-dosed gastric cell viability were investigated using human gastric carcinoma cells (Kato III) and normal rat gastric mucosa cells (RGM1). Addition of 2% and 3 % ethanol to Kato III and RGM1 cells, respectively, decreased their cell viability by approximately 20-50 % after 24 or 72 h of cultivation. In 2 % ethanol-dosed Kato III cells cultivated for 24 h, addition of 0.002-20 µg/mL D- and L-GA calcium did not affect cell viability. Similarly, addition of less than 20 µg/mL DL-GA calcium did not affect cell viability. However, when 20 µg/mL DL-GA calcium was added, cell viability increased by 35.7 % after 72 h of incubation, compared to the viability of control cells without ethanol or GA. Addition of 20 µg/mL DL-GA calcium to 3 % ethanol-dosed RGM1 cells cultivated for 24 or 72 h also increased cell viability up to those observed in control cells. These results suggest that a racemic mixture of GA may have the strongest effect on enhancing the viability of ethanol-exposed cells.

AHNAK expression and subcellular localization in gastric surface epithelial cells

We have previously demonstrated the expression of AHNAK protein in normal human organ donor stomach tissues. In order to identify the specific cells that express AHNAK in human stomach, we performed immunohistochemistry. We evaluated the subcellular localization and movement of AHNAK protein by immunohistochemistry, sucrose density gradient centrifugation, and Western blot analysis using specific AHNAK and subcellular marker antibodies. AHNAK immunoreactivity was localized to PAS, Alcian Blue, MUC5A positive gastric surface epithelial cells in normal human organ donor stomachs. Normal rat gastric mucosa (RGM1) cells demonstrated strong cytoplasmic staining for AHNAK. AHNAK protein was found predominately in the cytoplasmic fraction under standard culture conditions of RGM1 cells. AHNAK is often described as a nuclear phosphoprotein that translocates to the plasma membrane where it is involved in signal transduction, cell membrane differentiation, and repair. Further investigation and understanding of the potential recruitment of AHNAK to the plasma membrane may allow for novel strategies to regulate specific signaling cascades and induce membrane repair in gastric surface epithelial cells. This research was supported by an American Heart Association Predoctoral Fellowship and a Veterans Affairs Merit grant.

The C type natriuretic peptide receptor associates with AHNAK in human aortic vascular smooth muscle cells

We recently identified AHNAK as a binding partner for the C type natriuretic peptide receptor (NPR‐C) in normal rat gastric mucosa (RGM1) cells. To investigate the role of AHNAK in NPR‐C function in different cell types and species we examined the expression and interaction of both proteins in multiple cell lines. Antibodies to NPR subtypes and AHNAK domains were used to examine expression by immunoblotting, colocalization by immunohistochemistry, and interaction by immunoprecipitation in multiple mammalian cell lines. Mass spectrometry was used to confirm the identity of the proteins from the immunoprecipitation studies. GST fusion proteins of the N‐terminal, internal repeating, and C‐terminal domains of AHNAK were purified and used to perform GST pulldown assays to verify the association of the two proteins and determine specificity. Coding sequences of human NPR‐C and AHNAK were subcloned into mammalian two hybrid expression vectors to ascertain the interaction in situ. NPR‐C was found to be the most abundantly expressed NPR subtype and AHNAK was found to also be expressed in human aortic vascular smooth muscle cells (AoVSMCs). NPR‐C and AHNAK colocalized to the plasma membrane of AoVSMCs. NPR‐C bound to AHNAK isoform 1 in vitro. The interaction was attributed to a single AHNAK domain. This research was supported by an American Heart Association Predoctoral fellowship and a Veterans Affairs Merit grant.

Ticlopidine prevents the formation but delays the healing of ethanol-induced gastric lesions in the rat

The effects of acute or long-term oral ticlopidine administration in normal rat gastric mucosa or on gastric lesions induced by ethanol 50% (EtOH, 1 ml/rat, os) were examined and compared with those of acetylsalicylic acid (ASA). Ticlopidine does not affect gastric mucosal integrity either after acute (100 and 300 mg kg −1) or 1-week (100 mg kg −1, die) oral administration. Ticlopidine (30–300 mg kg −1, os) administered 1 h before EtOH dose-dependently prevented the development of gastric haemorragic lesions. When ticlopidine was administered 1 h after EtOH, it significantly ( p < 0.05) delays gastric lesions healing. Acute ASA (50 and 100 mg kg −1, os) administration causes a mild irritant activity similar to that observed after 1 week of ASA (50 mg kg −1, os/die) administration. In condition of mucosal damage, ASA does not modify either the induction or the healing of EtOH-induced gastric lesions. To assess the possible involvement of endogenous nitric oxide (NO) or prostaglandins (PG) in the gastric protective activity of ticlopidine, the rats were pretreated with an inhibitor of NO-synthesis, l-NAME (70 mg kg −1, s.c.) or the inhibitor of PG synthesis, indomethacin (Indo, 10 mg kg −1, s.c.). Indo, but not l-NAME, was able to significantly counteract the gastroprotective activity of ticlopidine against EtOH injury. Furthermore, ticlopidine increases (47%) gastric PGE 2 content in normal mucosa compared to the one detected in control rats, thus suggesting that endogenous PGs contribute to enhanced mucosal resistance by ticlopidine. These results indicate that ticlopidine exerts dual effects during the development and healing of gastric lesions induced by EtOH.

Influences of Helicobacter pylori on cyclooxygenase‐2 expression and prostaglandinE2 synthesis in rat gastric epithelial cells in vitro

It is known that cyclooxygenase (COX)-2 is over expressed in gastrointestinal neoplasia and Helicobacter pylori (H. pylori) infection is causally linked to gastric cancer. The present study aimed to elucidate the effects of H. pylori on COX-2 expression and prostaglandinE(2) (PGE(2)) production in a gastric epithelial cell line derived from normal rat gastric mucosa (RGM1). H. pylori water extracts were prepared from a supernatant of the H. pylori suspension in distilled water. RGM1 cells were cultured with H. pylori water extracts at the final concentration of 2.5, 5, 10 microg/mL for 24 h. For the time sequence study, RGM1 cells were cultured with 10 microg/mL H. pylori water extracts for 0, 6, 12, 24 and 48 h. COX-1 and COX-2 expression in the RGM1 cells was analyzed by western blotting. The levels of PGE(2) in the cultured media were measured by enzyme immunoassay. H. pylori did not affect COX-1 expression; whereas COX-2 expression increased by six-fold at 24 h after incubation of RGM1 cells with 10 microg/mL H. pylori water extracts. The increase in COX-2 expression was evident after 12 h of incubation; reached a peak at 24 h and declined at 48 h. H. pylori dose dependently increased COX-2 expression and PGE(2) synthesis in RGM1 cells. H. pylori induces COX-2 expression and increases PGE(2) synthesis in RGM1 cells in vitro. These results indicate that H. pylori-associated gastric carcinogenesis may depend on COX-2 expression.

Differential expression of CD95, Bcl-2, and Bax in rat gastric chief and parietal cells.

Apoptotic cell death is common in the inflamed gastric mucosa, but its role in the regulation of cell homeostasis in normal gastric mucosa is unknown. We investigated the expression of CD95, Bcl-2, and Bax and their roles in the regulation of apoptosis in normal rat gastric mucosa and in cultures of highly enriched rat chief and parietal cells by immunostaining, Western blotting, and FACS. In intact tissue CD95, Bcl-2, and Bax were localized predominantly in the glandular base region in chief cells. In freshly isolated cells, expression of CD95, Bcl-2, and Bax was much more pronounced in chief cells than in parietal cells. A lower intracellular Bcl-2/Bax ratio suggesting a higher susceptibility to apoptosis was noticed in chief rather than in parietal cells. In extended cultures of parietal and chief cells, Bax expression was upregulated and Bcl-2 expression was downregulated. These regulatory changes, presumably caused by in vitro effects, were not associated with an increase in spontaneous apoptosis. Treatment of chief and parietal cells with Fas-ligand induced apoptosis of all CD95 expressing cells. Expression of CD95, Bcl-2, and Bax predominantly in chief cells suggests that in this cell type regulation of apoptosis may differ from that in parietal cells. Binding of FasL with functionally active CD95 receptors on chief and parietal cells may be relevant for induction of apoptosis in inflamed gastric mucosa.

Role of cyclooxygenase isoforms in gastric mucosal defence

A complex system of interacting mediators exists in the gastric mucosa to strengthen its resistance against injury. In this system prostaglandins play an important role. Prostaglandin biosynthesis is catalysed by the enzyme cyclooxygenase (COX), which exists in two isoforms, COX-1 and COX-2. Initially the concept was developed that COX-1 functions as housekeeping enzyme, whereas COX-2 yields prostaglandins involved in pathophysiological reactions such as inflammation. In the gastrointestinal tract, the maintenance of mucosal integrity was attributed exclusively to COX-1 without a contribution of COX-2 and ulcerogenic effects of non-steroidal anti-inflammatory drugs (NSAIDs) were believed to be the consequence of inhibition of COX-1. Recent findings, however, indicate that both COX-1 and COX-2 either alone or in concert contribute to gastric mucosal defence. Thus, in normal rat gastric mucosa specific inhibition of COX-1 does not elicit mucosal lesions despite near-maximal suppression of gastric prostaglandin formation. When a selective COX-2 inhibitor which is not ulcerogenic when given alone is added to the COX-1 inhibitor, severe gastric damage develops. In contrast to normal gastric mucosa which requires simultaneous inhibition of COX-1 and COX-2 for breakdown of mucosal resistance, in the acid-challenged rat stomach inhibition of COX-1 alone results in dose-dependent injury which is further increased by additional inhibition of COX-2 enzyme activity or prevention of acid-induced up-regulation of COX-2 expression by dexamethasone. COX-2 inhibitors do not damage the normal or acid-challenged gastric mucosa when given alone. However, when nitric oxide formation is suppressed or afferent nerves are defunctionalized, specific inhibition of COX-2 induces severe gastric damage. Ischemia-reperfusion of the gastric artery is associated with up-regulation of COX-2 but not COX-1 mRNA. COX-2 inhibitors or dexamethasone augment ischemia-reperfusion-induced gastric damage up to four-fold, an effect abolished by concurrent administration of 16,16-dimethyl-PGE 2. Selective inhibition of COX-1 is less effective. Furthermore, COX-2 inhibitors antagonize the protective effect of a mild irritant or intragastric peptone perfusion in the rat stomach, whereas the protection induced by chronic administration of endotoxin is mediated by COX-1. Finally, an important function of COX-2 is the acceleration of ulcer healing. COX-2 is up-regulated in chronic gastric ulcers and inhibitors of COX-2 impair the healing of ulcers to the same extent as non-selective NSAIDs. Taken together, these observations show that both COX isoenzymes are essential factors in mucosal defence with specific contributions in various physiological and pathophysiological situations.

HGF triggers activation of the COX-2 gene in rat gastric epithelial cells: action mediated through the ERK2 signaling pathway.

Although it is established that growth factors and prostaglandins function in the maintenance of gastric mucosal integrity and in the healing of gastric mucosal injury and ulceration, the regulatory relationship between growth factors and prostaglandins in the gastric mucosa is not well characterized. Therefore, we investigated whether hepatocyte growth factor (HGF) affects expression of COX-2 (the inducible form of the prostaglandin synthesizing enzyme, cyclooxygenase) in gastric epithelial cells and whether this action is mediated through the MAP (ERK) kinase signaling pathway. In RGM1 cells (an epithelial cell line derived from normal rat gastric mucosa), HGF caused an increase in COX-2 mRNA and protein by 236% and 175%, respectively (both P<0.05). This induction of COX-2 expression was abolished by pretreatment with the MAPK kinase (MEK) inhibitor PD98059. HGF also triggered a 13-fold increase in c-Met/HGF receptor phosphorylation (P<0.005) and increased ERK2 activity by 684% (P<0.01). Pretreatment with PD98059 abolished the HGF-induced increase in ERK2 activity, but not c-Met/HGF receptor phosphorylation. The specific inhibitor of p38 MAP kinase, SB203580, had no effect on HGF-induced COX-2 expression. Thus, HGF triggers activation of the COX-2 gene in gastric epithelial cells through phosphorylation of c-Met/HGF receptor and activation of the ERK2 signaling pathway.-Jones, M. K., Sasaki, E., Halter, F., Pai, R., Nakamura, T., Arakawa, T., Kuroki, T., Tarnawski, A. S. HGF triggers activation of the COX-2 gene in rat gastric epithelial cells: action mediated through the ERK2 signaling pathway.

Rat gastric mucous gel layer contains sialomucin not produced by the stomach.

The sialylated mucus components of the normal gastric mucosa and mucous gel layer of rats were studied by using various histochemical staining methods including Maackia amurensis II (MAL-II) and Sambucus nigra (SNA) lectins, alcian blue (AB) pH 2.5 -- periodic acid Schiff (PAS) and high iron diamine (HID) -- AB pH 2.5. The acidic and neutral mucins characterized by the AB-PAS staining were abundantly present in the mucous gel layer as well as in the gastric mucosa. The sialomucin characterized by HID-AB was barely found in either the mucous gel layer or the mucosa. The sialomucin positive to MAL-II and SNA, which react with the N-acetyl neuraminic acid residue linked to galactose via an alpha-linkage, was moderately detected only in the mucous gel layer, but not in the entire mucosal layer. Furthermore, in animals given surgery to form an esophageal fistula through which saliva was excluded or in animals subjected to salivectomy, the mucous gel layer stained with MAL-II and SNA lectins was markedly decreased. These results indicate that a part of the sialomucin containing-mucous gel layer covering normal rat gastric mucosa originates from the saliva and that MAL-II and SNA lectins are useful for detecting this specific sialomucin.

Induction of cyclooxygenase-2 in a rat gastric epithelial cell line by epiregulin and basic fibroblast growth factor.

Prostaglandins play an important role in maintaining gastric mucosal integrity. Cyclooxygenases (COX-1 and -2) are the key enzymes involved in prostaglandin synthesis. COX-2 expression in gastric epithelial cells remains a subject of controversy, and a possible regulation of gastric COX-2 by growth factors has not been explored. Therefore, we studied the effect of growth factors including epiregulin, basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) on expression of COX-2 in a gastric epithelial cell line (RGM1) derived from normal rat gastric mucosa. Cells were incubated with 10 or 100 ng/ml of EGF. epiregulin, bFGF, or VEGF for 1, 2, 3, 6, and 24 h. COX-2 mRNA expression was determined by RT-PCR using specific COX-2 primers and COX-2 protein expression was determined by Western blotting. This study showed that COX-2 mRNA and protein are expressed in the gastric epithelial RGM1 cell line and that epiregulin and bFGF (but not VEGF) significantly increase expression of COX-2 mRNA and protein. Because PGs play an important role in mucosal defense, this study suggests that some growth factors contribute to maintaining mucosal integrity via activation of the COX-2 gene.

Histone H3 messenger RNA in situ hybridization for identifying proliferating cells in formalin-fixed rat gastric mucosa.

To devise a more sensitive method for identifying proliferative cells in routinely formalin-fixed, paraffin-embedded tissues, we applied an in situ hybridization (ISH) technique for the detection of histone H3 mRNA in rat gastric mucosa and amplified the signal by a silver intensification method. ISH was performed using a Fluorescein-labelled, single-stranded DNA probe for the human histone H3 gene. To determine the optimal conditions for detecting H3 mRNA in rat gastric mucosa, we tested the effect of changing conditions, such as fixation time and digestion time, by a proteinase before hybridization. Next, the proliferation indices obtained using H3 ISH were compared with those obtained using bromodeoxyuridine (BrdU) immunohistochemistry. In normal rat gastric mucosa, H3 ISH- and BrdU-positive cells were confined to the neck region of both fundic and pyloric mucosa. The two labelling indices were almost the same. In all the serial sections studied, H3 ISH-positive cells were almost always BrdU-positive too. Taken together, these results indicate that the H3 ISH technique is useful for the evaluation of proliferative activity in gastric epithelial cells by virtue of its detection of S-phase cells.

Oncofetal mucin Ml epitope family: Characterization and expression during colonic carcinogenesis

The gastric mucin M1 antigens, markers associated with colonic carcinogenesis, have been characterized by new antimucin monoclonal antibodies (MAbs). These MAbs, obtained against mucins isolated from a human ovarian mucinous cyst (MAbs 19M1, 21M1 and 45M1) and from a pancreatic adenocarcinoma (MAb 96RA), were compared with 5 other anti-M1 mucin MAbs described previously, which characterized the a, b, c, d and e mucin M1 epitopes. Using immunoperoxidase, these new MAbs exclusively stained the surface gastric epithelium of normal human gastro-intestinal tract and reacted with fetal, precancerous and cancerous colonic mucosa, but not with normal colon. Immunoradiofixation studies showed that these new MAbs are directed against 3 epitopes (f, g and h) which are different from the a, b, c, d and e mucin M1 epitopes, though present on the same a immunoreactive high-molecular-weight components (greater than 1,000 kDa) with a density of 1.4 by CsCl-density-gradient ultracentrifugation. M1 antigenicity is characterized by a family of 8 different M1 epitopes which were destroyed with beta-mercaptoethanol (except for the f epitope), sensitive to a 5 hr trypsin treatment and resistant to 5 mM periodate (except for the h epitope). Some epitopes (b, c and d) showed increasing immunoreactivity after 20 mM periodate treatment, suggesting cryptic location. In rat-colon adenocarcinomas, M1 mucin epitopes were masked but could be decrypted using high periodate treatment, similar to normal rat gastric mucosa, thus suggesting the absence of drastic changes in the saccharide coat of the peptide mucin portion bearing M1 epitopes. Cryptic location, periodate resistance, sensitivity to protease and conformational behavior strongly suggest that the peptidic core of gastric (or fetal colonic) mucin plays a role in M1 immunoreactivity. Indeed, the resurgence of M1 antigens during colonic carcinogenesis is due to re-expression of the peptide core of gastric (or fetal colonic) mucins.

Histochemistry and cytochemistry of thiamine pyrophosphatase (TPP-ase 3.6.1.) in the rat gastric mucosa

The paper deals with the histochemical and cytochemical distribution of thiamine pyrophosphatase (TPP-ase 3.6.1.) in the normal rat gastric mucosa using the method of NOVIKOFF and GOLDFISCHER (1961). In light microscopy, activity was demonstrated only in the GOLGI apparatus of the foveolar mucous cells; in the other specialized gastric mucosal cells no activity was established. At electron microscopic level, the reaction product was localized in the membranes of the cisternae of the GOLGI apparatus of foveolar mucous cells, undifferentiated neck cells, parietal cells, chief cells and in endocrine cells. The reaction product was not found in the endoplasmic reticulum of any of the above mentioned types of cells with the exception of parietal cells. The deposits of the reaction product in the cytoplasmic membrane, in the capillary endothelium and on the surface of the plasma membrane of foveolar mucous cells represents the sites of activity of alkaline phosphatase. The examination of the TPP-ase in the gastric mucosa inables us to estimate the activity of the GOLGI apparatus of gastric mucosal cells in the norm and in different pathological conditions connected with its changes.

Histochemical localization of enzymes in the normal rat gastric mucosa using the technique of the semipermeable membranes and the other methods

In the paper we observed histochemically the distribution and activity of 16 enzymes in the normal rat gastric mucosa. The lysosomal enzymes were demonstrated by the method of semipermeable membranes (LOJDA 1972). At the proof of dehydrogenases aqueous and gel media were used. The parietal cells of the gastric mucosa contained a moderate activity of acid phosphatase, E-600 resistant esterase, and only a very slight activity of beta-glucuronidase and N-acetyl-beta-D-glucosaminidase. The macrophages of the interstice contained a high activity of beta-glucruonidase, acid phosphatase, E-600 resistant esterase and a low activity of N-acetyl-beta-D-glucosaminidase. The chief cells of the rat gastric mucosa, in contrast to the human, did not contain nonspecific esterase and also in them acid phosphatase was mostly lacking. The alkaline phosphatase was found only in the endothelium of the capillaries of the gastric mucosa. The parietal cells contained high activities of succinate dehydrogenase, alpha-glycerophosphate dehydrogenase, beta-hydroxybutyrate dehydrogenase, NADH tetrazolium reductase, a lower activity of NADPH tetrazolium reductase, as well as other soluable dehydrogenases. At the examination of dehydrogenases using aqueous as well as gel media with PMS during optimal short incubation periods, we found more and less active forms of parietal cells. The different oxidoreductase capacity of parietal cells in normal rat gastric mucosa can point to their unequal-functional load at the production of hydrochloric acid. The findings obtained are compared with the findings in older papers concerning different experimental animals and with the distribution of enzymes in the human gastric mucosa.