Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regulation of gastric somatostatin is linked to changes in gastric acidity, with a number of studies showing a good correlation between somatostatin secretion and gastrin-stimulated luminal acidity. However, gastrin may also have direct effects on somatostatin secretion independent of the concurrent acid status. We have examined the relative contribution of gastrin itself vs. gastric acid on the increase in somatostatin secretion observed after gastrin administration. Pentagastrin administered to conscious sheep for 2 h caused a 10- to 12-fold increase in both portal venous and peripheral jugular venous plasma somatostatin levels. This was associated with a decrease in gastric pH from 3.5 to 1.7. When the sheep were pretreated with the proton pump inhibitor omeprazole to prevent any change in gastric acidity, pentagastrin caused a similar increase in plasma somatostatin. The increase in somatostatin could also be produced by gastrin-17 infusions. Thus, these studies demonstrate that in the conscious animal gastrin can stimulate somatostatin independent of changes in gastric acidity. It is proposed that there is a negative feedback between somatostatin and gastrin, which may modulate the acid secretory response to gastrin.
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PMID:Regulation of somatostatin secretion by gastrin- and acid-dependent mechanisms. 168 34

In a series of 24 hour studies, intragastric acidity and plasma gastrin concentration were measured simultaneously in 46 healthy subjects before, during, and 24 to 48 hours after abrupt withdrawal of a histamine H2 receptor antagonist regimen. For 34 days subjects were given either cimetidine 800 mg at night (n = 8), ranitidine 150 mg twice daily (n = 10), ranitidine 300 mg at night (n = 12), nizatidine 300 mg at night (n = 8), or famotidine 40 mg at night (n = 8). All subjects responded to H2 blockade by a decrease in 24 hour intragastric acidity. Withdrawal of H2 blockade resulted in a significant rise in median nocturnal integrated intragastric acidity in 42 of 46 subjects (+36%; 95% CI +19, +55%) compared with prestudy values, but this rise was not associated with a significant change in the median integrated plasma gastrin concentration (+1%; 95% CI -12, +13%). A statistically significant rise in nocturnal acidity was observed after all regimens, except after dosing with famotidine. After stopping, median daytime integrated acidity and plasma gastrin concentrations in the whole group were raised, but not significantly: values were +15% (95% CI +4, +34%) and +5% (95% CI -2, +12%), respectively. A statistically significant increase in daytime acidity was observed only after dosing with ranitidine. In conclusion, intragastric hyperacidity occurs in most subjects after abrupt withdrawal of a histamine H2 receptor blocker, but this phenomenon is not associated with hypergastrinaemia.
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PMID:Rebound intragastric hyperacidity after abrupt withdrawal of histamine H2 receptor blockade. 168 65

Gastric acidity is influenced by systemic and local peptide effects. Previous work by others has shown that intraluminally secreted peptides may have a role in local control of gastric acidity; however, the response of these peptides to acute changes in gastric pH is unknown. To determine the effects of acute changes in pH on systemic and intraluminal peptide levels, 14 normal volunteers underwent placement of a nasogastric tube after an overnight fast. Blood and gastric fluid were analyzed on a control day, 2 hours after completion of 24 hours of aluminum-magnesium antacid therapy and after 24 hours of H2 blockade. Plasma and acid-alcohol-extracted gastric peptide levels were measured with specific radioimmunoassays. Specimens were subdivided into two groups: 28 gastric fluid specimens with a pH less than 4 and 10 specimens with a pH greater than 4. In the patients with a pH greater than 4, the luminal peptides, motilin, neurotensin, pancreatic polypeptide, somatostatin, substance P, and gastrin, were decreased by 50% to 90% and gastrin-releasing peptide was decreased by 36% compared with specimens with a pH less than 4. Conversely, intraluminal vasoactive intestinal polypeptide and calcitonin levels were elevated by 60% and 27%, respectively, in the samples with a pH greater than 4. Intraluminal peptide concentrations are responsive to changes in intragastric pH; however, this response was not seen in plasma peptide levels.
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PMID:Acute gastric pH changes alter intraluminal but not plasma peptide levels. 172 Sep 3

Nine patients with Helicobacter pylori-related antral gastritis and history of duodenal ulceration were studied before and at 1 and 7 months after eradication of the infection by a 4-week course of tripotassium dicitrato bismuthate, metronidazole, and amoxycillin. The median basal gastrin concentration before eradication was 30 ng/l (range, 20-60) and fell to 20 ng/l (5-20) at 1 month (p less than 0.02) and 15 ng/l (5-20) at 7 months (p less than 0.01) after eradication. The integrated gastrin response to a peptide meal was 3650 ng/l.min (range, 1875-6025) before treatment compared with 1800 ng/l.min (range, 1200-3075) at 1 month (p less than 0.01) and 1312 ng/l.min (875-2625) at 7 months (p less than 0.03). Daytime intragastric pH (0900-2100 h) was similar before treatment (median, 1.4; range, 1.1-2.1) and at 1 month (1.4; 1.1-2.3) and 7 months (1.4; 1-2.2) after eradication. In five of the patients nighttime acid output (2300-0900 h) was also studied and was similar before (median, 86 mmol/10 h; range, 52-114) and at 1 month (76 mmol/10 h; 50-143) and 7 months (94 mmol/10 h; 63-106) after eradication. In conclusion, eradication of H. pylori is accompanied by a sustained fall in serum gastrin concentrations but is not accompanied by an early or late reduction of daytime intragastric acidity or nighttime acid output.
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PMID:Plasma gastrin, daytime intragastric pH, and nocturnal acid output before and at 1 and 7 months after eradication of Helicobacter pylori in duodenal ulcer subjects. 185 58

The antisecretory effects of H2-receptor antagonists are limited by food ingestion. The contributions of the cephalic-vagal and gastrinergic mechanisms to this interaction were examined in two 14-hour randomized, cross-over studies in 24 healthy volunteers. In the first study, either ranitidine or placebo was administered IV by a pH-feedback-controlled infusion pump during fasting, modified sham feeding, or food ingestion. Sham feeding resulted in a well-defined and abrupt interaction with the antisecretory effect of ranitidine (lasting 2-3 hours), after which fasting pH levels were regained. The second study, with the same design, showed that gastrin release occurred during this cephalic-vagal phase but was not attenuated by the additional infusion of the anticholinergic pirenzepine. Following eating, intragastric acidity increased and remained elevated for more than 6 hours. This increase was accompanied by prolonged hypergastrinemia, which was not diminished by pirenzepine. Pirenzepine did, however, enhance the antisecretory effect of ranitidine after both sham feeding and food ingestion. The interaction of food or sham feeding with the antisecretory effect of H2 antagonists is a consistent phenomenon. In both the cephalic-vagal and the gastric phases of secretion, this interaction appears to be partially mediated by a noncholinergic release of gastrin.
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PMID:The cephalic and gastric phases of gastric secretion during H2-antagonist treatment. 186 Jun 25

The reduction in intragastric acidity and the subsequent increase in plasma gastrin were compared during long-term treatment with either omeprazole or ranitidine in 19 patients with erosive reflux esophagitis. The patients received 40 mg omeprazole in the morning or 300 mg ranitidine twice daily. After healing, half the dose was given as maintenance treatment for 1 year. Intragastric acidity and plasma gastrin were measured 24 h before entry and monthly with the high dose and after 1, 6, and 12 months with the low dose. Omeprazole reduced intragastric acidity more effectively than ranitidine (p less than 0.001). This difference in efficacy was more pronounced during the daytime. Plasma gastrin increased more after omeprazole than after ranitidine (p less than 0.01), and both drugs showed a normal postprandial response and approached fasting levels before the next dose. During long-term treatment with 20 mg omeprazole in the morning no progressive alterations were observed in 24-h intragastric acidity or plasma gastrin.
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PMID:24-hour intragastric acidity and plasma gastrin during long-term treatment with omeprazole or ranitidine in patients with reflux esophagitis. 186

In a prospective study, eight young healthy subjects (five with an active H. pylori infection in the antral mucosa) were treated with a course of tripotassium dicitrato bismuthate, amoxycillin and metronidazole. The triple therapy eradicated infection when assessed 20-24 weeks later by antral biopsy (urease, histology, and 13C urea breath test [4 out of 5 subjects]). Twenty-four hour intragastric acidity and plasma gastrin concentration were measured before treatment, and 4-6 weeks and 20-24 weeks post-treatment. Treatment did not affect acidity in either the H. pylori-positive or H. pylori-negative groups, nor did it affect the plasma gastrin profile in the H. pylori-negative group. Eradication of H. pylori infection in five subjects caused a drop of the median integrated 24-hour plasma gastrin concentration from 558 pmol.h/L before treatment to 307 and 289 pmol.h/L at 4-6 and 20-24 weeks post-treatment, respectively. It is concluded that H. pylori infection is associated with 24-hour hypergastrinaemia, and that in apparently healthy subjects normal gastric physiology can be restored by eradication of the infection.
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PMID:Eradication of Helicobacter pylori abolishes 24-hour hypergastrinaemia: a prospective study in healthy subjects. 188 27

Repeated dosing with an H2-receptor antagonist results in a modest decrease in antisecretory potency termed "tolerance." The object of this prospective study was to determine whether tolerance is a progressive phenomenon or whether it levels off during prolonged dosing with a standard maintenance dose of an H2-antagonist. The effect of continuous dosing with ranitidine, 150 mg nightly, was compared with intermittent dosing (27 days of placebo each month) with active ranitidine, 150 mg nightly, only on the night of each experiment. Simultaneous 24-hour intragastric acidity and plasma gastrin concentration were measured monthly for 5 months in 17 healthy subjects (7 continuous and 10 intermittent dosing). In the intermittent-dosing group, the antisecretory response to ranitidine, 150 mg nightly, was preserved throughout the 141-day trial period; the median nocturnal integrated acidity decreased from 557 mmol.h/L (day 0) to 38 mmol.h/L on day 1 of dosing, and it ranged between 32 and 55 (median, 45) mmol.h/L during days 29-141. In the continuous-dosing group, there was a significant return of nocturnal intragastric acidity on days 29 and 85 compared with day 1 of dosing. The median nocturnal integrated acidity decreased in the continuous-dosing group from 554 mmol.h/L (day 0) to 87 mmol.h/L on the first day of dosing, and it ranged between 145 and 287 (median, 170) mmol.h/L during days 29-141. Either intermittent or continuous dosing with ranitidine was associated with an elevation of plasma gastrin concentration, which remained constant throughout the 5-month study. Tolerance does develop in healthy subjects during the first month of dosing with ranitidine, 150 mg nightly, but it is not a progressive phenomenon, and it is probably not of clinical relevance.
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PMID:Tolerance during 5 months of dosing with ranitidine, 150 mg nightly: a placebo-controlled, double-blind study. 188 19

We determined the effect of four times daily dosing with intravenous omeprazole on 24-h intragastric acidity, serum gastrin, and serum pepsinogen A and C in 10 fasting subjects (median age, 23.5 years). Two dose regimens (80-20-20-20 mg and 80-40-40-40 mg) were compared in a randomized placebo-controlled crossover study. Intragastric pH was continuously monitored during 24 h, using combined glass electrodes, and blood samples were taken every 6 h. Repeated boluses of omeprazole every 6 h significantly increased (p less than 0.01) the median 24-h intragastric pH compared with placebo (median pH, 3.7 (140 mg/day), 4.3 (200 mg/day), and 1.4 (placebo)) but failed to continuously raise pH levels above 4.0 in 8 (140 mg/day) or 9 (200 mg/day) of 10 subjects. No advantage of the 200-mg dose over the 140-mg dose was demonstrated. A cumulative effect of intravenous omeprazole was shown after repeated boluses but also a marked interindividual variation in response, which was correlated with the omeprazole area under the plasma concentration time curve. A significant elevation of serum gastrin coincided with the increased pH levels, which was followed after 12-18 h by a significant increase of both serum pepsinogens.
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PMID:Repeated intravenous bolus injections of omeprazole: effects on 24-hour intragastric pH, serum gastrin, and serum pepsinogen A and C. 189 17

The acute effects of continuous intragastric administration of 1500 ml (4200 kJ/liter) of a polymeric and of a nonpolymeric formula on gastric function were studied in 15 healthy subjects. During 450 min 1500 ml, containing 6300 kJ (1500 kcal), was given through a nasogastric tube. At regular intervals the volume, the pH, the titratable acidity, and the pepsin activity of the gastric contents and the plasma gastrin concentration were determined. Maximal observed intragastric volumes occurred after 120 min (118 +/- 16 ml during polymeric formula, 212 +/- 37 ml during nonpolymeric one) and volumes subsequently halved (at 450 min 68 +/- 13 and 104 +/- 16 ml, respectively). During the administration of both polymeric and the nonpolymeric formula intragastric pH fell progressively to 3.15 and 2.67, respectively, at 450 min. Incremental plasma gastrin values increased between 120 and 450 min from 7 to 12 ng/liter during the polymeric formula. During the nonpolymeric one it stabilized after 120 min at 12 ng/liter. When the whole test periods were considered integrated, mean intragastric volumes tended to be larger during the nonpolymeric formula (153 +/- 23 ml) than during the polymeric formula (107 +/- 12 ml), but this difference was not statistically significant. Median integrated mean pH was lower during the nonpolymeric formula (2.89) compared with the polymeric one (3.26). Despite the limitation that the investigations were performed in healthy subjects only, it is concluded from this study that the risk of aspiration during continuous nasogastric tube feeding is probably greatest during the first few hours of administration because of the larger intragastric volumes.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Acute effects of continuous nasogastric tube feeding on gastric function: comparison of a polymeric and a nonpolymeric formula. 190 Nov 12


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