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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is generally believed that the reduction in plasma [HCO3] characteristic of chronic hypocapnia results from renal homeostatic mechanisms designed to minimize the alkalemia produced by.the hypocapneic state. To test this hypothesis, we have induced chronic hypocapnia in dogs in which plasma [HCO3] had previously been markedly reduced (from 21 to 15 meq/liter) by the prolonged feeding of HCl. The PaCO2 of chronically acid-fed animals was reduced from 32 to 15 mm Hg by placing the animials in a large environmental chamber containing 9% oxygen. In response to this reduction in PaCO2, mean plasma [HCO3] fell by 8.6 meq/liter, reaching a new steady-state level of 6.4 meq/liter. This decrement in plasma [HCO3] is almost identical to the 8.1 meq/liter decrement previously observed in normal (nonacid-fed) animals in which the same degree of chronic hypocapnia had been induced. Thus, in both normal and HCl-fed animals, the renal response to chronic hypocapnia causes plasma [HCO3] to fall by approximately 0.5 meq/liter for each millimeter of Hg reduction in CO2 tension. By contrast, the response of plasma [H+] in the two groups was markedly different. Instead of the fall in [H+] which is seen during chronic hypocapnia in normal animals, [H+] in HCl-fed animals rose significantly from 53 to 59 neq/liter (pH 7.28-7.23). This seemingly paradoxical response is, of course, an expression of the constraints imposed by the Henderson equation and reflects the fact that the percent fall in [HCO3] in the HCl-fed animals was greater than the percent fall in PaCO2. These findings clearly indicate that in chronic hypocapnia the kidney cannot be regarded as the effector limb in a homeostatic feedback system geared to the defense of systemic acidity.
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PMID:Regulation of acid-base equilibrium in chronic hypocapnia. Evidence that the response of the kidney is not geared to the defense of extracellular (H+). 0 88

Predictable hydrolysis of [3H]digoxin-12alpha occurred in vitro with incubation in HCl or gastric juice. Hydrolysis varied with pH, time, temperature and agitation. Digoxin, the bis- and mono-digitoxosides of digoxigenin and digoxigenin were separated by silica gel thin-layer chromatography using chloroform-ethyl acetate-glacial acetic acid (25:25:1 v/v) and were quantitated by liquid scintillation spectrometry. Hydrolysis with incubation at 37 degrees and pH 3 for 90 min was minimal, but increased with increasing acidity until greater than 70% was hydrolysed at pH 1-2 after 30 min and greater than 96% after 90 min incubation. At pH 0-9, 87% was hydrolysed after 30 min. In vitro hydrolysis in gastric fluid was slightly less than in HCl at the same pH. A volunteer was given 150 muCi[3H]digoxin-12alpha by nasogastric tube during a pentagastrin infusion when gastric pH was 0-94. He remained on his left side and samples were aspirated at intervals and immediately neutralized. Ethanol-chloroform 50-50 (v/v) extracts of the gastric fluid aspirated after 90 min and of all the urine specimens collected for 5 days were applied to a DEAE Sephadex LH-20 column. The radioactivity appeared in a single peak as digoxigenin in the 90 min gastric aspirate and in all urine specimens. Extensive intragastric hydrolysis of digoxin may occur under conditions of maximum acid output.
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PMID:Hydrolysis of digoxin by acid. 1 78

It has generally been thought that homeostatic mechanisms of renal origin are responsible for minimizing the alkalemia produced by chronic hypocapnia. Recent observations from this laboratory have demonstrated, however, that the decrement in [HCO(-) (3)], which "protects" extracellular pH in normal dogs, is simply the by-product of a nonspecific effect of Paco(2) on renal hydrogen ion secretion; chronic primary hypocapnia produces virtually the same decrement in plasma [HCO(-) (3)] in dogs with chronic HCl acidosis as in normal dogs (Delta[HCO(-) (3)]/DeltaPaco(2) = 0.5), with the result that plasma [H(+)] in animals with severe acidosis rises rather than falls during superimposed forced hyperventilation. This observation raised the possibility that the secondary hypocapnia which normally accompanies metabolic acidosis, if persistent, might induce an analogous renal response and thereby contribute to the steady-state decrement in plasma [HCO(-) (3)] observed during HCl feeding. We reasoned that if sustained secondary hypocapnia provoked the kidney to depress renal bicarbonate reabsorption, the acute salutary effect of hypocapnia on plasma acidity might be seriously undermined. To isolate the possible effects of secondary hypocapnia from those of the hydrogen ion load, per se, animals were maintained in an atmosphere of 2.6% CO(2) during an initial 8-day period of acid feeding (7 mmol/kg per day); this maneuver allowed Paco(2) to be held constant at the control level of 36 mm Hg despite the hyperventilation induced by the acidemia. Steady-state bicarbonate concentration during the period of eucapnia fell from 20.8 to 16.0 meq/liter, while [H(+)] rose from 42 to 55 neq/liter. During the second phase of the study, acid feeding was continued but CO(2) was removed from the inspired air, permitting Paco(2) to fall by 6 mm Hg. In response to this secondary hypocapnia, bicarbonate concentration fell by an additional 3.0 meq/liter to a new steady-state level of 13.0 meq/liter. This reduction in bicarbonate was of sufficient magnitude to more than offset the acute salutary effect of the hypocapnia on plasma hydrogen ion concentration; in fact, steady-state [H(+)] rose as a function of the adaptive fall in Paco(2), Delta[H(+)]/Delta Paco(2) = -0.44. That the fall in bicarbonate observed in response to chronic secondary hypocapnia was the result of the change in Paco(2) was confirmed by the observation that plasma bicarbonate returned to its eucapnic level in a subgroup of animals re-exposed to 2.6% CO(2). These data indicate that the decrement in plasma [HCO(-) (3)] seen in chronic HCl acidosis is a composite function of (a) the acid load itself and (b) the renal response to the associated hyperventilation. We conclude that this renal response is maladaptive because it clearly diminishes the degree to which plasma acidity is protected by secondary hypocapnia acutely. Moreover, under some circumstances, this maladaptation actually results in more severe acidemia than would occur in the complete absence of secondary hypocapnia.
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PMID:The maladaptive renal response to secondary hypocapnia during chronic HCl acidosis in the dog. 2 Nov 98

We examined 66 patients with pain of possible esophageal origin for sensitivity to intraesophageal infusions of coffee, orange juice, spicy tomato drink, or HCl of varying concentrations as an addendum to their acid infusion (Bernstein) tests. Compared to Berstein-negative subjects, acid-sensitive patients were sensitive to infusion of coffee (P less than 0.01), orange juice (P less than 0.001), and tomato drink (P less than 0.001). Patients were largely insensitive to HCl solutions with a titratable acidity of 1 mEq per liter or less, less than the least acidic food solution tested. However, Berstein-positive patients were still highly sensitive to infusions of coffee, orange juice, and tomato drink adjusted to pH 7 (P less than 0.001). Patients were unable to differentiate symptoms caused by acid or food infusions, and solutions did not differ in the duration of infusion needed either to cause symptoms or to relieve them by saline. We conclude that the pain of esophagitis is nonspecific and can be precipitated by variety of seemingly unrelated substances.
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PMID:Food sensitivity in reflux esophagitis. 2 14

A basic premise in the utilization of the plasma anion gap in the assessment of acid-base disorders is that this parameter remains constant during hyperchloremic metabolic acidosis and metabolic alkalosis. Experimental data under in vitro conditions, however, cast serious doubt on this premise. The purpose of the present study was to characterize the plasma anion gap, estimated as (Na + K) - Cl + HCO3), in two large groups of dogs with graded degrees of chronic, HCl-induced metabolic acidosis or chronic, diuretic-induced metabolic alkalosis. The data indicate that the plasma anion gap decreases significantly in HCl acidosis and increases significantly in metabolic alkalosis; the predicted mean anion gap in animals with a plasma bicarbonate concentration of 10, 21 (normal), and 40 meq/liter approximated 13, 18, and 26 meq/liter, respectively. The observed variation in the plasma anion gap is interpreted as originating mainly from directional changes in the net negative charge of plasma proteins; these changes result from the titration process secondary to the altered plasma acidity and, in the case of metabolic alkalosis, from the additional effect of an increased plasma protein concentration.
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PMID:Changes in the plasma anion gap during chronic metabolic acid-base disturbances. 2 93

Intramural pH of the gastric mucosa was measured using a microelectrode technique in rabbit gastric pouches under different secretory conditions and luminal acidity. Exposure of spontaneously secreting or metiamide-treated fundic pouches to a relatively high concentration of luminal acid. HCl 120 mM, for 60 min, led to a marked net loss of luminal H+ which was associated with a significant decrease in the intramural pH (7.28 +/- 0.09 to 6.88 +/- 0.10 and 7.23 +/- 0.07 to 6.99 +/- 0.09, respectively). A linear relationship was observed between the rates of net disappearance of luminal acid and the intramural pH. All 10 spontaneously secreting and five metiamide-treated pouches had superficial mucosal erosions. In contrast, when fundic pouches were exposed to luminal acid in histamine-treated animals, the net loss of luminal H+ was negligible and the intramural pH remained at its base-line level (7.25 +/- 0.07). Histamine stimulation without acid in the lumen caused a small but insignificant increase in the intramural pH (7.27 +/- 0.03 to 7.39 +/- 0.05). Only three of the eight histamine-treated fundic pouches had lesions. In the antral pouches the intramural pH changes in response to exposure to luminal acid were smaller and histamine treatment did not influence the intramural pH. None of the antral pouches had lesions. The results suggest that acidification of the tissue by the diffusion of luminal acid may be an important factor in the pathogenesis of acute gastric ulceration. The acid secretory state of the gastric mucosa can significantly influence the acid-base balance in the mucosa and thus modify its response to acid diffusing from the lumen. Histamine stimulation protected the gastric mucosa by improving its buffering capacity and/or otherwise decreasing the diffusion of H+ from the lumen into the mucosa.
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PMID:Effect of the acid secretory state on intramural pH of rabbit gastric mucosa. 3 Jun 70

Effect of synthetic prostaglandin PGF2 alpha on the volume acidity, and proteolytic activity of the abomasum juice in sheep. Act Physiol. Pol., 1979, 30 (2): 299--304. The investigations were carried out in 3 male sheep on the effect of Estrumate (a synthetic analogue of PGF2 alpha) on the secretion and composition of juice from the "small" abomasum. After intramuscular injection of optimum doses of the preparation (3.0--4.0 micrograms/kg of body weight) it was observed that the volume of the juice, its free HCl content, the total acidity the specific activity (expressed in Anson milliunits/ml) and the total activity (specific activity X volume of juice secreted in a given sample) increased significantly (p less than 0.01). Thus, the synthetic prostaglandin PGF2 alpha stimulates the secretory activity of abomasum glands in sheep.
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PMID:Effect of synthetic prostaglandin PGF2 alpha on the volume, acidity, and proteolytic activity of the abomasum juice in sheep. 3 95

The influence of severe exocrine pancreatic disease on the acid-neutralizing capacity of the duodenum was studied in five patients with pancreatic insufficiency (PI) and six control subjects using duodenal perfusion-marker technique. Hydrochloric acid (0.1 N containing 1% PEG) was infused at constant rates (1.2, 4.5 and 7.0 ml/min) into the duodenum just distal to the duodenal bulb. Samples were aspirated from the tip of the duodenal perfusion tube located at the ligament of Treitz. All samples were analyzed for volume, pH, titrable acidity, PEG and [14C]PEG (gastric marker) determination. Patients with PI demonstrated significantly diminished ability to neutralize various acid loads as compared to controls who virtually completely neutralized acid loads in the range of maximal gastric acid secretion. Exogenous secretin did not significantly improve percent acid neutralized in PI. These data clearly indicate that patients with PI have significantly impaired ability to neutralize even small loads of acid in the duodenum.
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PMID:Impaired acid neutralization in the duodenum in pancreatic insufficiency. 3 15

Thirty-two hormonal polypeptides and nine proteins (8-65 kD) have been used to evaluate the potential of high-performance liquid chromatography on alkylsilane-bonded silica for separating and recovering biologically active compounds of this type. The basic method used was gradient elution with acetonitrile in an acid phosphate buffer. Variation of key chromatographic parameters demonstrated that low pH (less than 4.0) and high buffer molarity (greater than 0.1 M) are mandatory for reproducible high efficiency polypeptide chromatography. Simple NaCl-HCl mixtures of appropriate acidity and molarity could be substituted for the acid phosphate buffer, with the advantage of minimising non-physiological ion contributions to eluted materials. Minor selective effects were noted with different organic modifiers, but variation of other parameters, including choice of specific alkylsilane packings, did not materially influence separations. Under optimal conditions all of the polypeptides tested could be efficiently chromatographed, and many simultaneously resolved, as could most of the proteins tested. Three of the more hydrophobic proteins could not, however, be eluted from the alkylsilane packings. Retention orders of smaller compounds (less than 15 residues) generally correlated with the sum of the Rekker fragmental constants of their strongly hydrophobic residues. Larger polypeptides showed numerous anomalies when ranked by this means, however, limiting its predictive value. The separation of at least eighteen discrete components from a partially-purified posterior pituitary extract has demonstrated the capability of alkylsilane-type reversed-phase packings for the hydrophobic high-performance liquid chromatography of complex biological mixtures.
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PMID:Hydrophobic high-performance liquid chromatography of hormonal polypeptides and proteins on alkylsilane-bonded silica. 4 7

Pulmonary aspiration of gastric contents during general anesthesia has always been a serious problem. Morbidity and mortality depend on the volume and acidity of the aspirated material. The anesthetic agent itself might affect gastric acid secretion. The effect of halothane (5, 10 and 20 mg/kg intravenously) on HCl secretion and cAMP content of gastric juice in pyloric and cardiac ligated male Sprague-Dawley rats was investigated. Compared with the control group, halothane significantly increased both HCl secretion and cAMP content of gastric juice, but to a lesser degree at the higher doses (p less than 0.05).
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PMID:Hydrochloric acid and cyclic 3'.5'-adenosine monophosphate content of rodent gastric juice after halothane administration. 20 86


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