Biomedical subjects

J R Goldenring

Publications and source records attributed to J R Goldenring.

At least 37 records · Page 2Linked to original sources

PubMed1998

Identification of clathrin and clathrin adaptors on tubulovesicles of gastric acid secretory (oxyntic) cells.

gamma-Adaptin and clathrin heavy chain were identified on tubulovesicles of gastric oxyntic cells with the anti-gamma-adaptin monoclonal antibody (MAb) 100/3 and an anti-clathrin heavy chain MAb (MAb 23), respectively. In Western blots, crude gastric microsomes from rabbit and rat and density gradient-purified, H-K-ATPase-rich microsomes from these same species were immunoreactive for gamma-adaptin and clathrin. In immunofluorescent labeling of isolated rabbit gastric glands, anti-gamma-adaptin and anti-clathrin heavy chain immunoreactivity appeared to be concentrated in oxyntic cells. In primary cultures of rabbit oxyntic cells, the immunocytochemical distribution of gamma-adaptin immunoreactivity was similar to that of the tubulovesicular membrane marker in oxyntic cells, the H-K-ATPase. Further biochemical characterization of the tubulovesicular gamma-adaptin-containing complex suggested that it has a subunit composition that is typical of that for a clathrin adaptor: in addition to the gamma-adaptin subunit, it contains a beta-adaptin subunit and other subunits of apparent molecular masses of 50 kDa and 19 kDa. From solubilized gastric microsomes from rabbit, gamma-adaptin could be copurified with the major cargo protein of tubulovesicles, the H-K-ATPase. Thus this tubulovesicular coat may bind directly to the H-K-ATPase and may thereby mediate the regulated trafficking of the H-K-ATPase at the apical membrane of the oxyntic cell during the gastric acid secretory cycle. Given the similarities of the regulated trafficking of the H-K-ATPase with recycling of cargo through the apical recycling endosome of many epithelial cells, we propose that tubulovesicular clathrin and adaptors may regulate some part of an apical recycling pathway in other epithelial cells.

Adaptor Protein Complex beta Subunits↗

PubMed1998

Rab11a redistributes to apical secretory canaliculus during stimulation of gastric parietal cells.

Previous investigations in several systems have demonstrated that Rab3 family members redistribute to soluble fractions on fusion of secretory granules with target plasma membranes. Rab proteins are then recycled back onto mature secretory vesicles after reinternalization of the membrane. Although this cycle is well established for Rab3, far less is known about redistribution of other Rab proteins during vesicle fusion and recycling. In the gastric parietal cell, Rab11a is associated with H-K-ATPase-containing tubulovesicles, which fuse with the apical plasma membrane (secretory canaliculus) in response to agonists such as histamine. We have analyzed distribution of Rab11a and other tubulovesicle proteins in resting and histamine-stimulated rabbit parietal cells. Stimulation of isolated gastric glands in the presence of 100 microM histamine and 100 microM 3-isobutyl-1-methylxanthine did not cause a significant increase in soluble Rab11a. H-K-ATPase, Rab11a, Rab25, syntaxin 3, and SCAMPs increased immunoreactivity in stimulus-associated vesicles prepared from rabbits treated with histamine compared with those from ranitidine-treated animals. The large GTPase dynamin was found in both vesicle preparations, but there was no change in amount of immunoreactivity. Immunofluorescence staining of resting and histamine-stimulated primary cultures of parietal cells demonstrated redistribution of H-K-ATPase and Rab11a to F-actin-rich canalicular membranes. Dynamin was present on canalicular membranes in resting and stimulated cells. These results indicate that Rab11a does not cycle off the membrane during the process of tubulovesicle fusion with the secretory canaliculus. Thus Rab11a may remain associated with recycling apical membrane vesicle populations.

1-Methyl-3-isobutylxanthine↗

PubMed1998

Localization and significance of pp55, a gastric mucosal membrane protein with tyrosine kinase activity.

In Fischer 344 rats, induction of gastric mucosal proliferative activity, whether the result of aging or injury or occurring after administration of epidermal growth factor, gastrin, or bombesin, is associated with a rise in tyrosine kinase activity and tyrosine phosphorylation of several mucosal proteins, including a protein with a molecular mass of 53-55 kDa. We hypothesized that this phosphotyrosine membrane protein (referred to as pp55) may play a role in regulating gastric mucosal cell proliferation and differentiation. Purification and subsequent immunoprecipitation studies now show that pp55 is a tyrosine kinase. In addition, the enzyme activity in the gastric mucosa is found to be fourfold higher in aged rats than in young rats. Incubation of gastric mucosal membranes with transforming growth factor-alpha (2 x 10(-8) M) stimulates tyrosine kinase activity of pp55. Immunolocalization studies reveal that pp55 immunoreactivity is predominantly present in mucous cells that are located just above the proliferative zone and spasmolytic peptide-immunoreactive mucous neck cells. Tyrosine kinase activity as well as expression of pp55 are also greatly increased in the gastric mucosa after hypertonic saline-induced injury, a condition that results in stimulation of surface mucosal cell proliferation and differentiation. Our current data suggest that pp55 is a tyrosine kinase, likely localized to pre-surface cells. The presence of pp55 in pre-surface mucous cells and the expression and tyrosine kinase activity of this protein, which can be stimulated during mucosal cell proliferation and differentiation, strongly suggest a role for pp55 in differentiation of gastric surface mucous cells.

Aging↗

PubMed1997

Rab11 is associated with transferrin-containing recycling compartments in K562 cells.

3'RACE PCR was used to survey Rab transcripts synthesized by the human hematopoietic K562 cell line. Among the identified GTP-binding proteins, Rab11 was discovered. This result was unexpected since Rab11 previously had been found associated with polarized and secretory cells. Rab11 mRNA was abundant compared to that for other Rabs in K562 cells; protein levels represented 0.05-0.1% of total membrane protein. Localization of Rab11 using confocal immunofluoresence microscopy revealed extensive overlap with transferrin in recycling and/or exocytic compartments and suggests that Rab11 in non-polarized and non-secretory cells may play a role in the trafficking and recycling of internalized proteins.

Cell Compartmentation↗

PubMed1997

Two Rab proteins, vesicle-associated membrane protein 2 (VAMP-2) and secretory carrier membrane proteins (SCAMPs), are present on immunoisolated parietal cell tubulovesicles.

The tubulovesicles of gastric parietal cells sequester H+/K+-ATPase molecules within resting parietal cells. Stimulation of parietal cell secretion elicits delivery of intracellular H+/K+-ATPase to the apically oriented secretory canaliculus. Previous investigations have suggested that this process requires the regulated fusion of intracellular tubulovesicles with the canalicular target membrane. We have sought to investigate the presence of critical putative regulators of vesicle fusion on immunoisolated gastric parietal cell tubulovesicles. Highly purified tubulovesicles were prepared by gradient fractionation and immunoisolation on magnetic beads coated with monoclonal antibodies against the alpha subunit of H+/K+-ATPase. Western blot analysis revealed the presence of Rab11, Rab25, vesicle-associated membrane protein 2 (VAMP-2) and secretory carrier membrane proteins (SCAMPs) on immunoisolated vesicles. The same cohort of proteins was recovered on vesicles immunoisolated with monoclonal antibodies against SCAMPs and VAMP-2. In contrast, whereas immunoreactivities for syntaxin 1A/1B and synaptosome-associated protein (SNAP-25) were present in gradient-isolated vesicles, none of the immunoreactivity was associated with immunoisolated vesicles. The observation of VAMP-2 and two Rab proteins on immunoisolated H+/K+-ATPase-containing tubulovesicles supports the role for tubulovesicles in a regulated vesicle fusion process. In addition, the presence of SCAMPs along with Rab11 and Rab25 implicates the tubulovesicles as a critical apical recycling vesicle population.

Amino Acid Sequence↗

PubMed1997

Cyclic nucleotide-dependent vasorelaxation is associated with the phosphorylation of a small heat shock-related protein.

Activation of cyclic nucleotide-dependent signaling pathways leads to the relaxation of various smooth muscles. One of the major phosphorylation events associated with cyclic nucleotide-dependent vasorelaxation in bovine trachealis and carotid artery smooth muscle is the phosphorylation of two 20-kDa phosphoproteins with pI values of 5.7 and 5.9 (previously designated pp8 and pp3, respectively). The present studies sought to determine the identities of pp3 and pp8 in vascular smooth muscle. The phosphopeptide maps for the pp8 and pp3 proteins were similar. Preparative two-dimensional gel electrophoresis and amino acid sequencing of a peptide fragment of the pp3 protein revealed a sequence identical to a 20-kDa heat shock-related protein (HSP20) previously purified from skeletal muscle. Western blot and immunoprecipitation analysis with anti-HSP20 antibodies demonstrated that the pp3 and pp8 proteins are phosphorylated forms of HSP20. In addition, HSP20 could be phosphorylated in vitro by both cAMP-dependent protein kinase and cGMP-dependent protein kinase. These data suggest that the phosphorylation of the heat shock-related protein HSP20 is associated with cyclic nucleotide-dependent relaxation of vascular smooth muscle.

Animals↗

PubMed1997

Identification and characterization of a novel A-kinase-anchoring protein (AKAP120) from rabbit gastric parietal cells.

The type-II cAMP-dependent protein kinase (A-Kinase) partitions primarily into the particulate fraction in gastric parietal cells. Localization of this kinase to particular subcellular domains is mediated through the binding of the regulatory subunit (RII) dimer to A-Kinase-anchoring proteins (AKAPs). Using a [32P]RII overlay assay, we have screened a rabbit gastric parietal cell cDNA library and have isolated a single RII-binding protein clone. Sequence analysis revealed an open reading frame coding for 1022 amino acids (AKAP120). Recombinant fragments of the full-length clone were prepared and the RII-binding region mapped to an area between amino acids 489 and 549. This area contained a putative alpha-helical RII-binding region between amino acids 503 and 516. Incubation of [32P]RII with a synthetic peptide of AKAP120-(489-522) completely inhibited the binding of [32P]RII to the recombinant AKAP120 fragments that demonstrated RII binding. In vitro RII-binding affinity studies indicated a high-affinity interaction between AKAP120 and RII with a Kapp between 50 and 120 nM for the three recombinant fragments that bound [32P]RII. RNase-protection analysis revealed that AKAP120 is a widely distributed protein, with the highest levels of mRNA observed in gastric fundus. The presence of this novel high-affinity AKAP in gastric parietal cells suggests that it may regulate RII subcellular sequestration in this cell type.

Amino Acid Sequence↗

PubMed1997

Ezrin is a cyclic AMP-dependent protein kinase anchoring protein.

cAMP-dependent protein kinase (A-kinase) anchoring proteins (AKAPs) are responsible for the subcellular sequestration of the type II A-kinase. Previously, we identified a 78 kDa AKAP which was enriched in gastric parietal cells. We have now purified the 78 kDa AKAP to homogeneity from gastric fundic mucosal supernates using type II A-kinase regulatory subunit (RII) affinity chromatography. The purified 78 kDa AKAP was recognized by monoclonal antibodies against ezrin, the canalicular actin-associated protein. Recombinant ezrin produced in either Sf9 cells or bacteria also bound RII. Recombinant radixin and moesin, ezrin-related proteins, also bound RII in blot overlay. Analysis of recombinant truncations of ezrin mapped the RII binding site to a region between amino acids 373 and 439. This region contained a 14-amino-acid amphipathic alpha-helical putative RII binding region. A synthetic peptide containing the amphipathic helical region (ezrin409-438) blocked RII binding to ezrin, but a peptide with a leucine to proline substitution at amino acid 421 failed to inhibit RII binding. In mouse fundic mucosa, RII immunoreactivity redistributed from a predominantly cytosolic location in resting parietal cells, to a canalicular pattern in mucosa from animals stimulated with gastrin. These results demonstrate that ezrin is a major AKAP in gastric parietal cells and may function to tether type II A-kinase to a region near the secretory canaliculus.

Amino Acid Sequence↗

PubMed1997

Gastrin deficiency results in altered gastric differentiation and decreased colonic proliferation in mice.

BACKGROUND & AIMS: Gastrin is a peptide hormone important in the regulation of both acid secretion and differentiation of oxyntic mucosal cells of the stomach. To further elucidate the role of gastrin in the growth and development of the gastrointestinal tract, we have generated mice that are deficient in gastrin. METHODS: Gastrin-deficient mice were generated through targeted gene disruption. Gastric and colonic architecture were determined by routine histology and immunohistochemical techniques. Proliferation was assessed by 5-bromo-2'-deoxyuridine incorporation. RESULTS: Targeted disruption of the gastrin gene resulted in mice incapable of expressing gastrin messenger RNA (mRNA) or producing gastrin peptide. This deficiency led to a marked change in gastric architecture, with a decrease in number of parietal and enterochromaffin-like cells and an increase in number of mucous neck cells. There was no difference in the proliferation labeling index of the stomach in gastrin-deficient mice (3.04% +/- 0.33%) compared with wild-type littermates (3.15% +/- 0.18%). The colon of gastrin-deficient mice seemed normal histologically, although there was a decreased proliferation labeling index (2.97% +/- 0.52%) compared with wild-type littermates (4.71% +/- 0.44%; P < 0.01). CONCLUSIONS: Gastrin is important in regulating the differentiation of the gastric mucosa and is a trophic factor for the colonic mucosa.

Animals↗

PubMed1997

Inhibition of parietal cell acid secretion is mediated by the classical epidermal growth factor receptor.

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) inhibit gastric acid secretion both in vivo and in vitro. Previous studies have indicated that EGF and TGF-alpha bind to the same EGF/TGF-alpha receptor. Nevertheless, we and others have previously demonstrated that inhibition of acid secretion by these growth factors requires concentrations of the peptides that are 10-fold higher than those necessary for induction of mitogenesis. Therefore, we have sought to investigate whether gastric parietal cells may possess a second EGF/TGF-alpha receptor class. Two systems were studied: First, [125I]TGF-alpha was cross-linked to the receptor in isolated rabbit parietal cell membranes, and labeled species were resolved on SDS-PAGE. Second, acid secretion was evaluated in pylorus-ligated waved-2 mutant mice, which carry a disabling point mutation in their classical EGF/TGF-alpha receptor. In isolated parietal cells, [125I]TGF-alpha was cross-linked into a single species of 170 kDa. Cross-linking was inhibited in the presence of unlabeled TGF-alpha with an IC50 of 80 nM. In the pylorus-ligated mice, control littermate mice demonstrated a dose-dependent inhibition of acid secretion by EGF with an IC50 of 20 micrograms/kg. In contrast, EGF had no inhibitory effect on acid secretion in waved-2 mice at concentrations up to 100 micrograms/kg. No alterations in parietal cell or gastrin cell numbers were observed. These results in both isolated rabbit parietal cells and waved-2 mice support the existence of only a single class of EGF/TGF-alpha receptors in parietal cells. Differences in growth factor affinity are likely due to the modification of the receptor or one of its coordinate regulators.

Animals↗

PubMed1997

Increased immunoreactivity for Rab11, a small GTP-binding protein, in low-grade dysplastic Barrett's epithelia.

Adenocarcinoma of the esophagus develops from metaplastic Barrett's columnar epithelia through the evolution of dysplastic epithelial intermediates. Although the role of dysplasia leading to adenocarcinoma is well established, far less is known regarding the cellular changes involved in this process. Because the development of dysplasia is characterized by the loss of apical secretory specializations, we hypothesized that changes in apical trafficking might be involved in the dysplastic process. We have sought to evaluate the expression of an important candidate regulator of apical trafficking, the small GTP-binding protein, Rab11, in resection and biopsy tissue from patients with Barrett's esophagus. Sections from esophageal resection specimens from 4 patients and endoscopic biopsies from 60 patients were stained with antibodies against Rab11 and Rab25 as well as protein markers of the Golgi apparatus and p53 protein. Rab11 staining in low-grade dysplastic regions was similar to that observed with monoclonal antibodies against Rab25 and gamma-adaptin and colocalized with staining for the Golgi marker, the mannose-6-phosphate receptor. In the esophageal adenocarcinoma resections, prominent Rab11 immunostaining was observed in the supranuclear region of low-grade dysplastic cells. In contrast, regions of high-grade dysplasia demonstrating strong nuclear p53 staining showed only diffuse or absent Rab11 staining. In endoscopic biopsies, 91% of biopsies that were read unanimously as low-grade dysplasia demonstrated supranuclear Rab11 staining. Fourteen percent of biopsies unanimously graded as being without dysplasia demonstrated perinuclear Rab11 staining. No p53 immunostaining was observed in any of the low-grade dysplasia biopsy specimens. An increase in Rab11 immunoreactivity seems to correlate with low-grade dysplasia, whereas p53 immunostaining correlates with high-grade dysplasia. The colocalization of Rab11 staining with increased immunoreactivity for markers of the trans-Golgi system is consistent with a defect in apical trafficking due to an expansion of either the trans-Golgi compartment or the apical recycling vesicle system.

Barrett Esophagus↗

PubMed1996

Purification, cloning, and expression of a novel, endogenous, calcium-sensitive, 28-kDa phosphoprotein.

In gastric parietal cells, cholinergically induced increases in intracellular free calcium concentrations have been well characterized, but little is known about the signaling events beyond the initial rise in intracellular calcium. In the present study, we report the isolation of a 28-kDa protein, which is rapidly phosphorylated in intact, enriched parietal cells in response to both the cholinergic agonist, carbachol, and the calcium ionophore, ionomycin. A combination of in situ 32P labeling and one- and two-dimensional gel electrophoresis was used to acquire sufficient quantities of protein to obtain partial amino acid sequence. Cloning of the pp28 cDNA revealed a novel protein which we have named CSPP28 based on its calcium-sensitive phosphorylation. There are three CSPP28 mRNA species (1.7, 2.2, and 3.3 kilobases) that are widely distributed throughout a variety of rabbit tissues. Recombinant CSPP28 was phosphorylated by both crude parietal cell homogenate and purified CaM kinase II in a calcium/calmodulin-dependent manner. We propose that CSPP28 may play an important and ubiquitous role in the calcium signaling pathway.

Amino Acid Sequence↗

PubMed1996

A somatodendritic distribution of Rab11 in rabbit brain neurons.

Comparisons of subcellular targeting in neurons and epithelial cells have led to suggestions that apical epithelial antigens localize to axons and nerve terminals. We have studied the distribution in brain of the small GTP-binding protein, Rab11, which is localized to apical vesicular populations in epithelial cells. Sections of rabbit brain were examined by immunohistochemistry using a monoclonal antibody against rabbit Rab11. Rab11 immunoreactivity was present exclusively in neurons. In all regions examined, including forebrain, cerebellum, thalamus and brainstem, Rab11 immunoreactivity was observed in cell bodies and dendrites. No staining was observed in hippocampal neurons. These results indicate that the distribution of Rab11 does not support previous suggestions that apical epithelial markers should localize to axons and synaptic endings.

Animals↗

PubMed1996

Genetic ablation of parietal cells in transgenic mice: a new model for analyzing cell lineage relationships in the gastric mucosa.

The gastric mucosa of mammalian stomach contains several differentiated cell types specialized for the secretion of acid, digestive enzymes, mucus, and hormones. Understanding whether each of these cell lineages is derived from a common stem cell has been a challenging problem. We have used a genetic approach to analyze the ontogeny of progenitor cells within mouse stomach. Herpes simplex virus 1 thymidine kinase was targeted to parietal cells within the gastric mucosa of transgenic mice, and parietal cells were ablated by treatment of animals with the antiherpetic drug ganciclovir. Ganciclovir treatment produced complete ablation of parietal cells, dissolution of gastric glands, and loss of chief and mucus-producing cells. Termination of drug treatment led to the reemergence of all major gastric epithelial cell types and restoration of glandular architecture. Our results imply the existence of a pluripotent stem cell for the gastric mucosa. Parietal cell ablation should provide a model for analyzing cell lineage relationships within the stomach as well as mechanisms underlying gastric injury and repair.

Animals↗

PubMed1996

Foveolar hyperplasia following partial gastrectomy results from expansion of surface mucous cell compartment.

Antrectomy with gastroenterostomy reconstruction is often associated with the development of foveolar hyperplasia and oxyntic atrophy. While a role for bile reflux in the etiology of foveolar hyperplasia is well established, the identity of the mucous cell lineages responsible for this condition have not been well characterized. We have studied three patients who demonstrated foveolar hyperplasia in their gastric remnant following antrectomy and gastroenterostomy. Mucosal samples were stained with antibodies against the trefoil peptides pS2 and hSP, to identify surface mucous and mucous neck cell lineages, respectively. Postoperative biopsies from all three patients showed oxyntic atrophy as documented by staining of parietal cells with antibodies against H/K-ATPase. All three patients demonstrated an exclusive expansion of pS2 immunoreactive mucous cells. The hSP staining cells were located deep in the expanded foveolar region. The results suggest that foveolar hyperplasia following antrectomy with gastroenterostomy results from a reactive hyperplasia of surface mucous cells. This pattern of surface cell hyperplasia is more consistent with a reactive expansion of mucous cells than with a response to chronic injury.

Adult↗

PubMed1996

Overexpression of transforming growth factor-alpha alters differentiation of gastric cell lineages.

Overexpression of transforming growth factor-alpha (TGF-alpha) in the gastric fundic mucosa of metallothionein promoter/enhancer-TGF-alpha(MT-TGF-alpha) transgenic mice produces a phenotype of foveolar hyperplasia similar to that observed in Ménétrier's disease. We have investigated the dynamics involved in the alterations of gastric mucosal morphology in the MT-TGF-alpha mouse model. The fundic mucosa of MT-TGF-alpha mice and nontransgenic littermates was evaluated in animals treated with cadmium sulfate. To mark the mucosal proliferative zone, 8-bromodeoxyuridine (BrdU) was administered 2 hr prior to killing. Gastric mucosa was examined by diastase-resistant, periodic acid-Schiff-positive (DR-PAS) staining and immunohistochemistry for H/K-ATPase an BrdU. MT-TGF-alpha mice demonstrated increased numbers of DR-PAS-staining mucous cells and lower parietal cell numbers per gland unit. While the proliferative zone in nontransgenic mice was located in the upper half of the gland, the zone in MT-TGF-alpha mice was located in the basal region. Overexpression of TGF-alpha in MT-TGF-alpha mice leads to an alteration in the development of mucosal lineages from the fundic progenitor zone, which is biased towards the predominant differentiation of foveolar mucous cells.

Animals↗

PubMed1996

Rab11 is an apically located small GTP-binding protein in epithelial tissues.

Rab proteins are involved in many aspects of dynamic vesicle processing within eukaryotic cells. We have previously identified Rab11 in gastric parietal cell tubulovesicle membranes. We have produced a monoclonal antibody that is specific for Rab11. In all rabbit tissues examined, Rab11 immunoreactivity was highly enriched in epithelial cells. In the gastric fundus, parietal cells were stained in a pattern consistent with localization on tubulovesicles. Surface mucous cells of both the fundus and antrum demonstrated punctate subapical staining. Ileal and proximal colonic enterocyte labeling was observed deep to the brush borders. In the distal colon, staining was observed in the apical regions of mid-crypt cells. In skin and esophagus, punctate immunoreactivity was present in the medial layers of the squamous epithelia. Prominent Rab11 immunoreactivity was present in hepatocytes deep to the bile canaliculi. Punctate subapical staining was observed in pancreatic acinar cells. Apical staining was also observed in collecting duct cells and in the glandular cells of the prostate. These results indicate the Rab11 is expressed in apical vesicular populations in discrete epithelial cell populations.

Animals↗

PubMed1996

Evidence for a regulatory role for histamine in gastric enterochromaffin-like cell proliferation induced by hypergastrinemia.

BACKGROUND/AIMS: Hypergastrinemia, induced by sustained suppression of gastric acid secretion, is associated with gastric enterochromaffin-like (ECL) cell hyperplasia and carcinoid tumor formation. We examined the effect of a selective H1-histamine antagonist, terfenadine, on gastric mucosal cell proliferation to determine whether histamine might modulate ECL cell generation. METHODS: The rodent mastomys received the H2-antagonist loxtidine (2 g/l drinking water) alone or in combination with terfenadine (0.5 g/l or 35 mg/l drinking water) for 120 days. Controls received water or terfenadine alone. Serum gastrin levels and tissue histamine content were assayed by radioimmunoassays, and tissue chromogranin levels determined (Western blot analysis). In vivo cell proliferation was measured by bromodeoxyuridine (BrdU, 200 mg/kg/day, 3 days) incorporation. Gastric mucosal thickness was determined, ECL cell number was assessed, and the percentage of proliferating ECL cells quantitated. To evaluate the direct action on ECL cells we then studied the effect of terfenadine on histamine secretion and DNA synthesis (BrdU uptake) in an isolated preparation (approximately 90% pure) of ECL cells. RESULTS: Loxtidine increased serum gastrin levels, mucosal thickness, tissue chromogranin levels, tissue histamine content, BrdU incorporation, ECL cell number, and proliferating ECL cells (all parameters p < 0.05). Terfenadine alone, irrespective of dosage, had no significant effect. The high dose in combination with loxtidine significantly inhibited the increase in tissue chromogranin levels, tissue histamine content, ECL cell number and proliferating ECL cells (p < 0.05), but did not alter other parameters, compared to loxtidine alone. The low does did not alter the loxtidine-induced changes. In pure isolated ECL cells, terfenadine did not alter histamine secretion either alone or in combination with gastrin (10 nM). DNA synthesis was significantly inhibited by terfenadine (IC50 10(-10) M). CONCLUSIONS: Terfenadine specifically inhibited the effect of loxtidine-induced ECL cell proliferation in vivo and significantly inhibited ECL cell DNA synthesis in vitro. We postulate that histamine, through an H1 receptor, positively modulates gastric ECL cell proliferation.

Animals↗