NaOH) with an automatic titrator (Radiometer, Copenhagen, Denmark). Gastric acid secretion was determined during a 2- (pentagastrin and histamine) or 1-h period (somatostatin and galanin). To compensate for the differences in basal secretion, in some cases, the acid response was calculated as net acid output (i.e. difference between total gastric acid output during the time considered and the rate of basal secretion during the same period). gene on a 129 Sv/C57BL6 hybrid background (17). Wild-type and knockout mice were genotyped by Southern blot analysis and knockout mice maintained as inbred colonies.
How Is Acid Reflux Disease Diagnosed?
PACAP-27 and -38 dose-dependently raise [Ca2+]i in ECL cells, and stimulated histamine release. VIP had a much lower affinity, which demonstrates the presence of PAC1 but not VPAC. PACAP elevated [Ca2+]i in ECL and parietal cells of superfused gastric glands, but only the parietal cell signal was inhibited by ranitidine, showing the absence of PAC1 on parietal cells, and demonstrating functional coupling between the cell types. PACAP and VIP stimulated calcium signaling and somatostatin release from D cells with almost equal efficacy.
It is then released in the small intestine where it is absorbed and travels to the parietal cells in the stomach via the circulation. The diffusion distances are then very short (micrometres) and the PPI is converted to its active form as soon as it reaches the acid space just outside the acid pump itself. It is then perfectly positioned to bind covalently to the H + /K + -ATPase on the parietal cell membrane. This binding is long lasting but is overcome by the synthesis of new pump molecules.
Initial activation of GAS is regulated by the CNS when food is smelled and tasted (10, 35). When food enters the stomach, mechanical or chemical receptors (i) initiate GAS via activation of afferent/efferent fibers connected to the CNS, (ii) stimulate the gastrin-producing G cells or the histamine-producing enterochromaffin-like cells, or (iii) directly stimulate the HCl-producing parietal cells. Caffeine stimulates GAS, and, so far, it has been assumed that it acts via inhibition of PDE or by antagonizing adenosine receptors in gastric parietal cells (1).
Furthermore, AG-1749 prevented gastric lesions induced by absolute ethanol or acidified aspirin, and accelerated the healing of acetic acid-induced gastric or duodenal ulcers in rats. The inhibitory potency of AG-1749 in dogs was much the same as that of omeprazole and about half that of ranitidine. However, it was about 2 to 10 times more potent than omeprazole and 4 to 34 times more potent than ranitidine in rats.
- Whether vagally stimulated acid secretion reflects an effect of the enteric nervous system on the ECL cells (neuropeptides) and/or a direct one on the parietal cells needs to be further investigated.
- Their pharmacological properties are much more similar than they are different.
- Before the intervention, the trial subjects had to fast from food and liquid for 10 h.
and wild-type mice were measured at 18 days, 9 weeks, and 6 months of age as described previously (14). Mice were euthanized 15 min after subcutaneous injection of histamine (2 Î¼g/g body weight) and the intact stomach was removed. Although the plasma half-lives of PPIs are quite short, their mechanism of action enables most patients to be satisfactorily treated with once-daily dosing. Generally it does not matter whether the dose is given in the morning or the evening.
is the receptor subtype that mediates the effects of somatostatin on gastric acid secretion (14, 15). The are a number of ways in which acid production can be decreased. The first of these is via accumulation of acid in the empty stomach between meals. This increase in acid leads to a lower pH within the stomach, which inhibits the secretion of gastrin, via the production of somatostatin from D cells.
Serum gastrin concentrations rose significantly whenever intragastric pH was raised. Serum gastrin also rose after MgCl2, AlCl3, and CaCl2 with a pH of 2, when intragastric pH was not significantly altered. This rise, however, was significantly smaller than after administration of the antacids, except in the MgCl2-Mg(OH)2 and in the CaCl2 pH 10-CaCO3 groups. No significant rise of serum gastrin levels was observed after BaSO4.
That assumption may be supported by a number of other conditions. For example, NO can easily penetrate cell membranes, which may indicate an intracellular site of action. Also, NO has a rather short life span, which implies that sources needed to generate this oxide must be available close to the NO target cell. In this study, the occurrence of eNOS in the glands is shown, but earlier extensive investigations using antibodies against both nNOS and iNOS have not revealed presence of any of the two isoforms in the glandular epithelium of normal human subjects (unpublished observation). Similar to results obtained in a study of isolated rabbit gastric glands, we found that the NOS inhibitors L-NAME and L-NNA, but not D-NAME, amplified the secretion-stimulating effect of histamine, which further indicates that the isolated human glands we used contained the enzyme NOS.
Coexpression of KCNE3/KCNQ1 in COS cells led to an acid-insensitive current; KCNE2/KCNQ1 was activated by low extracellular pH. ECL cells are numerous in the acid-producing part of the rat stomach.