Gastric acid secretion phases

Gastric acidity will also affect the absorption of medication. An acidic environment increases the absorption of weak acids, whereas the absorption of weak bases is facilitated by a less acidic environment. Many psychotropic agents such as tricyclic antidepressants (TCAs] and benzodiazepines are weak bases. Older studies of gastric acid secretion found that women have approximately 33%-40% lower basal gastric acid secretion than do men [Yonkers and Hamilton 1995]. Gastric acid secretion may be further decreased in the luteal phase of the menstrual cycle (Booth et al. 1957]. 

Gastrin CCK-B receptor 14- and 17-residue peptide amide with a Glu rich region Stimulate gastric acid secretion Solution-phase and solid-phase V -Fmoc chemistry... 

Feldman, M and Richardson, C. T. (1986). Rnic of thought, sight, smell, and taste of food in the cephalic phase of gastric acid secretion in humans Qi irocnlero ogy 90,428-433. 

Gastric acid secretion is stimulated by food-related signals that stimulate the release of acid from specialized cells within the stomach. This secretory process has been divided into three phases cephalic, gastric, and intestinal, with each phase leading to different amounts of acid being secreted (Table 3.3). 

Another program to obtain a reversible proton-pump inhibitor came from workers at SmithKline French, who selected the substituted quinoline compound SK F 96067 as an early clinical candidate (164). SKF 96067 is a reversible inhibitor of the H /K -ATPase protein of the parietal cell (164). In clinical trials SKF 96067 was found to be a more potent inhibitor of gastric acid secretion than the Hz-receptor antagonist ranitidine. This compound reached Phase III clinical trials but has now been discontinued (165). The compound was followed by SKF 97574 (159) that, although of similar potency to that of SKF 96067, displayed a significantly longer duration of action in vivo. 

Curling s ulcer (stress ulcer) is an acute ulceration of the stomach or duodenum that forms following a burn injury. Histamine2 antagonists like Pepcid are administered to decrease gastric acid secretion in the acute phase of bum care. 

Rabeprazole is a new PPI that has been approved for clinical use in Japan and is undergoing late-phase clinical trials in Europe and North America. Although rabeprazole was designed to be more potent than omeprazole for suppressing gastric acid secretion, it appears to dissociate more quickly and completely from H, K -ATPase than omeprazole or lansoprazole, suggesting a partially reversible inhibition of the proton pump [83]. Currently, published information on rabeprazole is scarce and mainly comes from animal studies and a limited number of studies performed in humans which have been published in abstract form only [83]. 

Gastric secretion and motility are controlled by both nervous and hormonal mechanisms. The vagus initiates the cephalic phase of secretion in response to the sight or smell of food, before food is eaten. The gastric phase occurs when food enters the stomach and is controlled both by intrinsic nerve reflexes in the stomach wall and released gastrin. The third, or intestinal, phase of secretion is coordinated by nervous and hormonal mechanisms to limit the release of the chyme from the stomach into the duodenum and reduces further acid secretion. 

Glucose-dependent insulinotropic polypeptide (GIP) GIP receptor 42-residue peptide Inhibit gastric acid and stimulate insulin secretion Solution-phase chemistry... 

The cephalic phase of digestion stimulates only a fraction of the maximum possible levels of gastric and pancreatic secretions. This phase does not seem to produce a rise in the levels of gastrin and CCK. Cephalic stimulation of the pancreas, as mediated by the vagus nerve, provokes release of pancreatic enzymes into the small intestine. Cephalic stimulation of the parietal cells, as mediated by the vagus nerve, provokes release of gastric acid into the lumen of the stomach- In humans, the cephalic phase does not seem to result in release of bicarbonate into the lumen of the small intestine. 

The basal rate of hydrochloric acid secretion varies diurnally, being highest in the evening and lowest in the morning. After ingestion of a meal, the rate of acid secretion in the stomach increases. The three phases of increased acid secretion in response to food are the cephalic phase (before food reaches the stomach), the gastric phase (elicited by the presence of food in the stomach), and the intestinal phase (elicited by input from the duodenum and upper jejunum). 

Gastric Phase. Gastrin is the main mediator of acid secretion. Acid secretion occurs h response to both the presence of nutrients and the physical distension produced by food entering the stomach. Distension-induced gas.-trie acid secretion, relative to the total amount of acid released, is species dependent (human = 20% dog = 50% rat = 38%). The chemical constituents of a meal are the strongest stimulant of gastrin release and acid output during... 

In their analysis of the chemical phase of gastric secretion, Pavlov s students found that meat extracts applied to the oxyntic mucosa do not stimulate acid secretion. Instead, Pavlov s students Savich and Zeljony showed before the First World War... 

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