The actions of secretagogues on oxygen uptake by isolated mammalian parietal cells.

The action of histamine, carbamylcholine, and gastrin on oxygen uptake by cells isolated from canine fundic mucosa was studied in vitro. Viable mucosal cells were prepared by exposure of separated mucosa sequentially to collagenase and EDTA. Oxygen consumption, determined by polarography, was chosen as an index of physiological response of mucosal cells to secretagogues. Isobutyl methyl xanthine (IMX), carbamylcholine, histamine, and gastrín each independently stimulated oxygen uptake by the unfractionated mucosal cells. The response to histamine was greatly enhanced when IMX was present. In fractions of varying parietal cell content obtained with the Beckman elutriator rotor, basal and stimulated oxygen uptake correlated with the parietal cell content of the fractions. The percentage increases in oxygen uptake in response to histamine, gastrin, carbamylcholine, and IMX were similar in enriched fractions with from 50 to 85% parietal cells and in unenriched starting fractions. The normalized dose-response relations for histamine with an IMX background and for carbamylcholine were also similar in these two fractions.The specificity of these responses was tested by use of an H(2)-histamine receptor antagonist, metiamide, and an anticholinergic agent, atropine. At the doses used, neither metiamide (0.1 mM) nor atropine (10 muM) inhibited basal oxygen uptake. Histamine, studied with an IMX background, was inhibited by metiamide but not by atropine, while carbamylcholine was inhibited by atropine but not by metiamide. Neither metiamide nor atropine inhibited gastrin-stimulated oxygen uptake. These data indicate that in this in vitro system parietal cells account for most of the increase in oxygen uptake produced by exposure to gastric secretagogues and that histamine, gastrin, and carbamylcholine each independently stimulate oxygen uptake by the parietal cell. The specificity displayed by atropine and metiamide in this in vitro system suggests that the parietal cell has specific receptors for each of these secretagogues.

The interaction of histamine with gastrin and carbamylcholine on oxygen uptake by isolated mammalian parietal cells.

Using oxygen uptake as an index of the physiological response of isolated parietal cells, the interactions between histamine and gastrin and between histamine and carbamylcholine and the effects of atropine and metiamide on these interactions have been studied. Parietal cells were isolated from canine fundic mucosa by sequential exposure of separated mucosa to collagenase and EDTA. In previous studies carbamylcholine, isobutyl methyl xanthine, gastrin, and histamine have each been shown to increase oxygen uptake by these cells. Isobutyl methyl xanthine greatly enhanced the histamine effect. Carbamylcholine was inhibited by atropine but not by metiamide, histamine was inhibited by metiamide but not by atropine, and gastrin was inhibited by neither, suggesting that each of these agents has a direct action on the parietal cell. In the present studies, potentiating interactions between histamine and carbamylcholine and between histamine and gastrin have been demonstrated. Against a histamine (0.1 and 1 muM) plus isobutyl methyl xanthine (0.1 mM) background, the dose for 50% response for gastrin was approximately 1 nM, and the maximal response was obtained at 0.1 muM. When added to these combinations of stimulants, metiamide and atropine retained their respective specificities against stimulation by histamine and carbamylcholine, in that responses were inhibited to the level that was seen when the component of the pair that was not inhibited was given alone. The observation that histamine plus gastrin and histamine plus carbamylcholine produced maximal responses that were greater than the maximal response to histamine alone further supports the hypothesis that these agents each have direct actions on parietal cells. These observations are not consistent with the hypothesis that histamine is the sole mediator for the effects of other secretagogues. Furthermore, the inhibitory effects of atropine and metiamide on the specific cholinergic and histaminic components of the interactions that occur between secretagogues provide a possible explanation for the apparent lack of specificity of these agents on in vivo acid secretion.

Specific inhibition by prostaglandins E2 and I2 of histamine-stimulated [14C]aminopyrine accumulation and cyclic adenosine monophosphate generation by isolated canine parietal cells.

The effects of prostaglandins E2 and I2 on accumulation of [14C]aminopyrine and the generation of cyclic AMP by fractions of dispersed canine gastric mucosal cells, enriched in their content of parietal cells, have been studied. The parietal cell content of the fractions was enriched to between 43 and 70% using an elutriator rotor. The accumulation of [14C]aminopyrine was used as the index of parietal cell response to stimulation. Prostaglandin E2 (PGE2, 0.1 nM-0.1 mM) inhibited histamine stimulated aminopyrine uptake but did not block the response to carbachol, gastrin, or dibuturyl cyclic AMP. PGE2 did, however, inhibit aminopyrine uptake stimulated by carbachol and gastrin when the response to these agents was potentiated by histamine. PGE2 (0.1 NM-0.1 mM) inhibited histamine-stimulated cyclic AMP production in a dose-dependent fashion with maximal inhibition at 1 microM PGE2. Prostacyclin also inhibited both histamine-stimulated aminopyrine accumulation and histamine-stimulated cyclic AMP production. In the absence of added histamine, PGE2 in concentrations above 1 microM and prostacyclin in concentrations above 10 microM stimulated cyclic AMP production, probably by acting on the nonparietal cells as shown in previous studies. These present data are consistent with the hypothesis that prostaglandins E2 and I2 inhibit the response of isolated parietal cells to histamine by specifically blocking histamine-stimulated cyclic AMP production.

Extracellular calcium and cholinergic stimulation of isolated canine parietal cells.

The role of calcium gating in cholinergic stimulation of the function of parietal cells was studied using cells isolated from canine fundic mucosa by treatment with collagenase and EDTA and enriched by velocity separation in an elutriator rotor. Monitoring the accumulation of [14C[ aminopyrine as an index of parietal cell response, stimulation by carbachol, but not by histamine, was highly dependent upon the concentration of extracellular calcium. Incubation of parietal cells in 0-.1 mM calcium, rather than the usual 1.8 mM concentration, reduced the response to 100 microM carbachol by 92 +/- 2%, whereas histamine stimulation was impaired by 28 +/- 5%. A similar reduction in extracellular calcium suppressed the response to gastrin (100 nM) by 67 +/- 7%. The impairment of cholinergic stimulation found at low extracellular calcium concentrations was rapidly reversed with the readdition of calcium. Lanthanum, which blocks calcium movement across membranes, caused a similar pattern of effects on secretagogue stimulation of aminopyrine accumulation, with 100 microM lanthanum suppressing carbachol stimulation by 83 +/- 2%. This concentration of lanthanum suppressed gastrin stimulation by 40 +/- 7% and histamine stimulation by only 12 +/- 9%. Carbachol, but not histamine nor gastrin, stimulated 45Ca++ uptake. The magnitude of carbachol-stimulated calcium uptake correlated with the parietal cell content of the fractions examined (r = 0.88), and was dose responsive over carbachol concentrations from 1 microM to 1 mM. Atropine (100 nM) caused surmountable inhibition, and these effects of carbachol and atropine on calcium uptake correlated with their effects on oxygen consumption (r = 0.93) and [14C]-aminopyrine accumulation (r = 0.90). Cells preloaded with 45Ca++ lost cellular calcium in a time-dependent fashion; however, this rate of egress was not accelerated by treatment with histamine, gastrin, or carbachol, thus failing to implicate mobilization of intracellular calcium as primary mechanism for activation of parietal cell function. These data indicate a close link between stimulation of parietal cell function and enhancement of calcium influx by cholinergic agents.

Stimulation of gastrin release by bombesin and canine gastrin-releasing peptides. Studies with isolated canine G cells in primary culture.

Bombesin, a polypeptide derived from frog skin, has been shown to stimulate gastrin release from the gastric antrum in vivo and in vitro. To elucidate the mechanisms of this effect, we developed a method to culture isolated and enriched G cells from canine stomach. After digestion of antral mucosa with collagenase and EDTA, dispersed cells were fractionated by counterflow elutriation then cultured on a collagen support. Bombesin and three molecular forms of canine gastrin-releasing peptides all stimulated gastrin release from G cells in a dose-dependent manner. The effect of bombesin was suppressed by somatostatin and potentiated by dibutyryl cyclic AMP (10(-3) M) but not by carbachol (10(-6) M). Extracellular calcium depletion attenuated the stimulation of gastrin release by bombesin but not by forskolin. These findings suggest that the bombesin family peptides directly activate G cells through calcium-dependent mechanisms to cause gastrin release.

Mitogenic response of canine fundic epithelial cells in short-term culture to transforming growth factor alpha and insulinlike growth factor I.

We report methods allowing the culture of rapidly dividing gastric epithelial cells to investigate the regulation of mucosal cell replication. Cells from canine fundic mucosa were dispersed by enzyme treatment, enriched by filtration and elutriation, and cultured on collagen gel in DMEM/F12 medium. After 48 h, greater than 95% of the cells displayed immunoreactivity with antibody to cytokeratin, an epithelial marker. The cells formed confluent monolayers by 72 h with a transmembrane resistance of 1,600 ohm.cm2 when mounted in a Ussing chamber indicating retention of epithelial cell characteristics. Calf serum (0.1-2%) produced a dose-dependent mitogenic effect evident by increases in [3H]-thymidine incorporation into acid-precipitated material and in cell number. After an 18-24-h incubation with [3H]-thymidine, approximately 55% of the cells cultured in 2% serum showed evidence of DNA synthesis by autoradiography and all of the replicating cells were cytokeratin positive. Using comparable culture conditions, a similar proportion of cells incubated for 18-24 h with bromodeoxyuridine displayed nuclear anti-bromodeoxyuridine immunoreactivity, thus indicating that over half of the cells in these cultures synthesized DNA during this period. As with serum, epidermal growth factor and transforming growth factor alpha (TGF alpha) (10 pM to 1 nM), insulin (10 nM to 1 microM) and insulinlike growth factor-I (IGF-I, 1-100 nM) increased [3H]-thymidine uptake. The greater potency of IGF-I, compared to insulin, suggests the presence of IGF-I receptors. We conclude that this culture preparation is composed of fundic mucosal epithelial cells and contains a predominance of dividing epithelial cells. EGF/TGF alpha and IGF-I are potential factors directly regulating proliferation of fundic mucosal cells.

Prostaglandin E2 production by dispersed canine fundic mucosal cells. Contribution of macrophages and endothelial cells as major sources.

Endogenous prostaglandins (PGs) influence resistance of the gastric mucosa to injury, but the source of PGs is unknown. Using radioimmunoassay, we studied PG production by dispersed canine fundic mucosal cells. PGE2 production, stimulated by bradykinin, epidermal growth factor, zymosan, and calcium ionophore, was greater in the small-cell elutriator fraction (SCEF) than in the medium and large cell fractions, which contained mucous, chief, and parietal cells. Linear density gradients of SCEF cells revealed maximal PGE2 production in cells of light density. Mast, endocrine, and endothelial cells did not account for this PGE2 production. Macrophages, identified by uptake of acetylated-LDL, immunoreactivity with antibodies to the human Ia antigen, and phagocytosis of fluorescent latex particles, were enriched in the SCEF and correlated with PGE2 production in the density gradient. Magnetic separation of cells in the SCEF-ingesting iron particles enriched PGE2 production. Fractions enriched in endothelial cells present in intact capillary fragments, but depleted of macrophages, also produced PGE2. Regulation of PGE2 production differed among cell types. Fibroblasts were easily cultured from submucosa, but were not detected in the SCEF. We conclude that macrophages and capillary endothelial cells are major producers of PGE2 in the canine fundic mucosa.

Gastrin receptors on isolated canine parietal cells.

The receptors in the fundic mucosa that mediate gastrin stimulation of acid secretion have been studied. Synthetic human gastrin-17-I (G17) with a leucine substitution in the 15th position ( [Leu15]-G17) was iodinated by chloramine T; high saturable binding was found to enzyme-dispersed canine fundic mucosal cells. 127I-[Leu15]-G17, but not 127I-G17, retained binding potency and biological activity comparable with uniodinated G17. Fundic mucosal cells were separated by size by using an elutriator rotor, and specific 125I-[Leu-15]-G17 binding in the larger cell fractions was highly correlated with the distribution of parietal cells. There was, however, specific gastrin binding in the small cell fractions, not accounted for by parietal cells. Using sequential elutriation and stepwise density gradients, highly enriched parietal and chief cell fractions were prepared; 125I-[Leu15]-G17 binding correlated positively with the parietal cell (r = 0.98) and negatively with chief cell content (r = -0.96). In fractions enriched to 45-65% parietal cells, specific 125I-[Leu15]-G17 binding was rapid, reaching a steady state at 37 degrees C within 30 min. Dissociation was also rapid, with the rate similar after 100-fold dilution or dilution plus excess pentagastrin. At a tracer concentration from 10 to 30 pM, saturable binding was 7.8 +/- 0.8% per 10(6) cells (mean +/- SE) and binding in the presence of excess pentagastrin accounted for 11% of total binding. G17 and carboxyl terminal octapeptide of cholecystokinin (26-33) were equipotent in displacing tracer binding and in stimulating parietal cell function ( [14C]aminopyrine accumulation), whereas the tetrapeptide of gastrin (14-17) had a much lower potency. Proglumide inhibited gastrin binding and selectively inhibited gastrin stimulation of parietal cell function. Canine parietal cells have specific receptors for gastrin that mediate stimulation of parietal cell function. Gastrin receptors were undetectable on chief cells, and yet present on another smaller mucosal cell(s).

A new approach to molecular configuration applied to aqueous pore transport.

A cylindrical treatment of the configuration of small molecules in solution has been proposed. Cylindrical dimensions were obtained from Fisher-Hirschfelder molecular models, and these dimensions were used in an analysis of three sets of reflection coefficient values from the literature. The correlation between solute dimensions and the reflection coefficient was subjected to both statistical analyses and graphical examination, with particular emphasis given to parameter interdependence. The results consistently indicated a significant relation between the reflection coefficient and solute diameter. The dependence on diameter suggests a lengthwise orientation of solute within the membrane. Furthermore it is shown that this orientation is occurring within the aqueous region of the membrane, and thus this region has a structural characteristic which is responsible for the lengthwise orientation of solute.

Prostanoid inhibition of canine parietal cells.

Cellular mechanisms underlying the anti-secretory actions of the prostaglandin E2 analogue enprostil were studied using enzyme-dispersed, elutriator-enriched canine parietal cells and the accumulation of the weak base 14C-labeled aminopyrine as a functional index. Enprostil inhibited the accumulation of aminopyrine stimulated by histamine and the phosphodiesterase inhibitor isobutylmethyl, but not by carbachol, gastrin, or dibutyryl cyclic adenosine monophosphate. Inhibition by enprostil was dose-dependent (0.1 nM to 1 microM), with maximal inhibition ranging from 65 to 95 percent. Over the same concentration range, enprostil inhibited the histamine-stimulated generation of cyclic adenosine monophosphate. This selective inhibition of histamine activation of parietal cell function was comparable to that found for prostaglandin E2. Forskolin, a diterpene that directly activates the catalytic subunit of adenylate cyclase, was also markedly inhibited by nanomolar concentrations of prostaglandin E2 and enprostil. We conclude that at least a component of the secretory inhibition by enprostil reflects direct interference with histamine stimulation of parietal cell adenylate cyclase.

Canine enteric submucosal cultures: transmitter release from neurotensin-immunoreactive neurons.

A culture system of dispersed submucosal neurons from canine ileum has been developed. The neuronal nature of over 80% of the cells in culture was confirmed by positive staining with a neurofilament antibody. In this culture system, neurotensin-immunoreactive neurons constituted greater than 50% of the total cell population. Neurotensin immunoreactivity in these cells was chromatographically characterized as a single molecular form coeluting with synthetic neurotensin (1-13). We have assessed the release of immunoreactive neurotensin by stimulatory and inhibitory transmitters, and by post-receptor activators of cell function. Forskolin (10 microM), the calcium ionophore A23187 (100 nM), and the active phorbol ester beta-12 myristrate 13-acetate (10 nM), each significantly increased neurotensin release compared with basal peptide secretion. The concomitant application of ionophore and phorbol ester resulted in a marked increase in neurotensin release and this stimulatory response was inhibited over 70% by somatostatin (100 nM). Substance P (0.1-100 nM) caused a dose-dependent increase in neurotensin release. Somatostatin (100 nM) reduced maximal stimulation with 100 nM substance P by 79%. Our results suggest that this submucosal culture system represents an entirely new model for characterizing transmitter release from enteric neurons.

Histamine synthesis in intact and disrupted rat mast cells.

Histamine production by purified intact rat peritoneal mast cells, as measured by formation of [beta-3H]histamine from [beta-3H]L-histidine or by release of 14CO2 from 14C-carboxyl-labeled histidine, was ten to thirty times greater than that of disrupted cells of soluble extracts of these cells. Loss of activity was evident whether cells were disrupted by sonification, freezing and thawing, or lysis, both in the absence and presence of inhibitors of proteolytic enzymes and agents known to preserve enzyme responsible for histamine formation in both the intact cells and cell extracts. In the presence of subsaturating concentrations of histidine, various histidine analogs and glutamine inhibited histidine data indicate that, at physiological concentrations of histidine, blockade of histidine transport (through system N) may limit histamine synthesis in the intact cell and that measurement of histidine decarboxylase activity in tissue homogenates or cell extracts may not reflect actual histidine decarboxylase activity in vivo.

Review: antisecretory drugs: cellular mechanisms of action.

Parietal cell secretory function may be inhibited by three mechanisms. (1) Receptors for gastrin, histamine and acetylcholine are present on the canine parietal cell, and parietal cell function may be directly inhibited by specific antagonists for each of these receptors. (2) Receptor activation of parietal cell function is mediated by cyclic AMP-dependent (histamine) and calcium-dependent (cholinergic agents and gastrin) mechanisms. The antisecretory action of prostaglandins reflect interference with histamine activation of adenylate cyclase. The current generations of calcium channel blockers have only weak antisecretory actions in vivo and are unlikely to be useful in clinical practice. (3) A third mechanism of inhibition is blockade of H+/K(+)-ATPase by substituted benzimidazoles, such as omeprazole. Each of these three mechanism provides modalities of potential clinical usefulness for treating acid-peptic disease. Gastrin and acetylcholine receptors are present on other fundic cells, in addition to the parietal cell. These other cells include the somatostatin cell in the dog fundic mucosa and the histamine-containing enterochromaffin-like (ECL) cell present in the fundic mucosa of several species. The relative impact of these receptors on different cell types on the regulation of acid secretion remains uncertain, and is probably variable among different species. One gastrin receptor of considerable importance is the gastrin receptor that exerts a trophic effect on the ECL cell in the fundic mucosa. Sustained hypergastrinaemia in response to profound hypochlorhydria is associated with hyperplasia of this cell type; the elucidation of the conditions that promote this hyperplasia and the clinical consequences of this association are pressing challenges.

Instantaneous and continuous measurement of 14C-labeled substrate oxidation to 14CO2 by minute tissue specimens: an ionization chamber method.

The vibrating reed electrometer and ionization chamber have been adapted for the instantaneous and continuous measurement of 14C-labeled substrate oxidation to 14CO2 by minute quantities of isolated tissues. This modified technique, utilizing a "closed" circulation incubation system, is 10-50 times as sensitive as the previously described "open" circulation techniques. Substrate oxidation curves are described for human erythrocytes and polymorphonuclear leucocytes, canine parietal cells and isolated segments of the rat nephron. This apparatus should prove to be a useful tool for metabolic studies of small quantities of isolated tissue.

Characterization of bombesin receptors on canine antral gastrin cells.

Dispersed canine antral mucosal cells were prepared by sequential steps of collagenase digestion and EDTA treatment. Cell preparations enriched in gastrin cells were made by centrifugal elutriation followed by step density gradient centrifugation. Specific, saturable, and reversible binding of 125I-[Tyr4]-bombesin was found in all preparations. This saturable binding was time, temperature, and cell number dependent. In both velocity (elutriator) and density cell separation experiments, saturable binding of bombesin correlated with the distribution of cells containing gastrin- but not somatostatin-like immunoreactivity. Maximal specific binding to gastrin (G) cell-enriched fractions was reached in 45 min at 37 degrees C and constituted 90% of total binding. Addition of 100 nM nonradioactive bombesin to cells incubated with 50 pM 125I-[Tyr4]-bombesin for 45 min resulted in time-dependent dissociation of specifically bound tracer to about 40% of the maximal equilibrium binding. Analysis of saturable equilibrium binding yielded a best fit to a one-site model of high affinity binding sites with an apparent Kd of 85 +/- 14 pM and a Bmax of 231,000 +/- 71,000 receptors/gastrin cell. Nonradioactive [Tyr4]-bombesin and related analogs inhibited the specific binding of the tracer in a dose-related manner. The rank order of potency, determined at the IC50, of [Tyr4]-bombesin and related analogs for inhibition of specific binding was bombesin greater than [Tyr4]-bombesin = hGRP-27 greater than GRP-10 greater than ranatensin much greater than neuromedin B. Cholecystokinin, somatostatin, substance K, and kassinin each tested at a concentration of 1 microM did not inhibit bombesin binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Somatostatin is released in response to cholecystokinin by activation of type A CCK receptors.

Cholecystokinin is a principal mediator of intestinal fat-induced inhibition of gastric acid secretion, indicating that it is an important physiological enterogastrone. Cholecystokinin has been shown to inhibit acid secretion by activation of type A CCK receptors and through a mechanism involving somatostatin. In the present study, we investigated the possibility that these two mechanisms are directly related such that activation of type A CCK receptors by CCK causes the release of somatostatin. We tested this hypothesis in vivo in a study of CCK-stimulated release of somatostatin in dogs and in vitro in a study of CCK-stimulated release of somatostatin from an enriched culture of canine fundic D cells. In dogs, IV infusion of CCK (50 pmol/kg/h, IV) significantly increased circulating somatostatin concentrations above basal. Further, systemic administration of somatostatin MAb F(ab)1 fragments of a somatostatin monoclonal antibody prevented most of CCK-induced inhibition of meal-stimulated acid secretion. In canine fundic D cells in culture, CCK-stimulated somatostatin release was blocked in a dose-dependent fashion by application of a type A CCK receptor antagonist. This study indicates that CCK activates type A CCK receptors to release somatostatin from canine fundic mucosal D cells, and accounts for somatostatin-dependent CCK-induced inhibition of acid secretion.

Future directions for reductionistic research in gastric secretion and defense.

Our theme centers on the complex processes that constitute and regulate the function of the gastric mucosa. Although some investigators promote the critical importance of a given element, such as acid, blood flow, or mucus, it is clear that both gastric secretory function and mucosal defense and repair mechanisms are multifactorial and are regulated by redundant control circuits. While it is true that critical studies can be performed in vivo with intact mucosa, at the same time it is frequently difficult, using these methods, to define the specific cellular elements involved in the regulation of secretion, defense, and repair. We now recognize that ulcer disease does not occur simply when this balance is thrown off. To the contrary, ulcer disease commonly occurs when the normal mucosal mechanisms are perturbed by Helicobacter pylori-associated gastro-duodenitis or nonsteroidal anti-inflammatory drugs. In the absence of such perturbation, the redundancy of the regulatory mechanisms underlying gastric secretion and the multiple lines of defense and healing would render ulcer disease rare indeed.

Multiple pathways controlling acid secretion.

A simple balance exists between factors that promote ulcer disease (e.g., acid and pepsin secretion) and factors that protect the stomach from ulcer disease (e.g., mucosal defense mechanisms). These factors are regulated and control the integrity of the gastric mucosa. Some of the newest discoveries in the area of regulation of acid secretion are related to the cellular localization of physiologically relevant receptors for acid secretagogues and acid inhibitors. The ability to isolate and culture histamine-containing ECL cells and somatostatin-containing "D" cells, and the ability to clone genes encoding for specific receptors has greatly enhanced our understanding of the physiological role and the regulation of various cell types within the gastric mucosa.

Peptic ulcer and dyspepsia.

Peptic ulcers are defects in the gastrointestinal mucosa that extend through the muscularis mucosae. They persist as a function of the acid or peptic activity in gastric juice. Twenty years ago, most ulcers were considered idiopathic; but a revolution in knowledge has occurred, so that it is now understood that the great majority of ulcers results from infection with Helicobacter pylori (HP) or use of nonsteroidal anti-inflammatory drugs (NSAIDs). Before this revolution, peptic ulcer disease was a common public health problem, responsible for considerable morbidity, some mortality, and high economic cost. Today, the overall prevalence of ulcers is falling, but complication rates remain relatively stable. These complex trends primarily reflect 3 factors: the rapid decline in the prevalence of HP in the population of developed countries, an increase in consumption of NSAIDs, and change in rates of smoking. Peptic ulcer prevalence is falling in younger individuals because of decreased prevalence of HP, whereas complications are rising in older subjects, largely as the result of increased NSAID use.

Gastroesophageal reflux: practical management of a common, challenging disorder.

Gastroesophageal reflux (GER) occurs in 2 distinct forms that differ in pathophysiology, clinical presentation, natural history, and therapy: mild GER (with no or minimal esophagitis) and classic, severe reflux (at risk for erosive esophagitis). A minority of subjects (< 20%) have the classic, potentially severe pattern of GER caused by reduced lower esophageal sphincter (LES) pressure and prolonged acid reflux, particularly at night, but also during the day. Evaluation and management must be catered to patients with this pattern of reflux. In contrast, symptoms in mild reflux (the majority) often occur during the day after meals in an upright posture (upright reflux); resting LES pressure is usually normal (reflux episodes are related to transient relaxation of the LES) and little reflux occurs at night. Acid reflux, which occurs mostly during the day, overlaps with the normal range and esophagitis is rare; however, symptoms can be distressing. Optimal management is controversial because no outcome trials have been conducted to address management in primary care settings. However, clinical clues can help differentiate mild and severe reflux and guide management decisions. This article provides a detailed approach to current management of GER syndromes.