Effect of gastric juice on iron absorption in patients with gastric atrophy

Is achlorhydria a cause of iron deficiency anemia?

We re-evaluated the old hypothesis that gastritis-induced achlorhydria is a cause of iron deficiency anemia (IDA) in humans. First, we analyzed the currently available research on the association between achlorhydria and IDA. When gastric acid secretion was measured after maximal stimulation, the frequency of achlorhydria (or severe hypochlorhydria) was 44% in patients with idiopathic IDA and 1.8% in healthy controls. In some patients with pernicious anemia, presumed achlorhydria preceded the development of IDA in time. However, we found no credible evidence that IDA caused gastritis or that IDA preceded the development of achlorhydria. Thus, correlational results favor achlorhydria as the causal factor in the association between achlorhydria and IDA. Second, we sought to determine whether gastritis and achlorhydria cause negative iron balance. When biosynthetic methods were used to isotopically label iron in food, achlorhydric patients were found to have severe malabsorption of nonheme iron, which persisted after the development of IDA. In 1 study, achlorhydria reduced the normal increase in heme-iron absorption from hemoglobin in response to iron deficiency. After an injection of isotopic iron into normal men, the physiologic loss of iron from the body was found to be 1 mg/d. Patients with chronic gastritis had excess fecal loss of isotopically tagged plasma iron. Calculations based on these results indicate that the absorption of iron from a typical Western diet by achlorhydric patients would be less than physiologic iron losses, creating a negative iron balance that could not be overcome by the adaptive increase in duodenal iron absorptive capacity that occurs in response to iron deficiency. The combination of results from these correlational and pathophysiologic studies supports the hypothesis that gastritis-induced achlorhydria can be an independent cause of IDA.

Management of experimental hypochlorhydria with iron deficiency by the composite extract of Fumaria vaillantii L. and Benincasa hispida T. in rat

The aim of the present study was to search the effective ratio of whole plant of Fumaria vaillantii Loisel (Fumaria vaillantii L.) and fruit of Benincasa hispida Thunb. (Benincasa hispida T.) in composite form, namely “FVBH” for the management of hypochlorhydria along with iron deficiency in male albino rats. Hypochlorhydria refers to suppression of hydrochloric acid secretion by the stomach. Hypochlorhydria was induced by ranitidine in this study. We used four composite extracts of the mentioned plant and fruit with different ratios (1:1, 1:2, 2:1, and 3:2) for searching the most effective composite extract for the correction of hypochlorhydria. Gastric acidity is an important factor for iron absorption. Thus, hypochlorhydria causes iron deficiency in rat and it was prevented significantly by the extract treatment at the ratio of 1:1 of the said plant and fruit. The correction of iron deficiency by the composite extract was compared with iron supplementation to hypochlorhydric rat. It was found that preadministration followed by coadministration of FVBH-1 (1:1) able to prevent the ranitidine-induced hypochlorhydria and iron deficiency. The composite extract, FVBH-1 (1:1) significantly (P<0.05) increased the pepsin concentration, chloride level in gastric juice, iron levels in serum and liver along with blood hemoglobin level than other ratios used here. Hence, it can be concluded that FVBH-1 (1:1) is an effective herbal formulation for the management of hypochlorhydria and related iron deficiency.

A new role for an old hormone: is gastrin a cofactor for dietary metal ion uptake?

It is proposed that gastrin promotes the uptake of divalent and trivalent metal ions from the gastrointestinal lumen by catalyzing the binding of metal ions to luminal albumin and transferrin respectively. The following observations are consistent with this hypothesis: 1. Gastrin binds both divalent and trivalent metal ions. 2. Gastrin binds to both albumin and apotransferrin. 3. Binding of gastrin to albumin is enhanced by divalent metal ions. 4. Gastrin, albumin and transferrin are all present in gastric juice. 5. Surgical removal of the gastric mucosa results in iron deficiency.

A role for mucin in the absorption of inorganic iron and other metal cations. A study in rats

The steps involved in iron absorption are poorly understood. Although transferrin and ferritin are water soluble, most radioiron in gut homogenates after an intraluminal dose of radioiron is recovered in water-insoluble precipitates. Most radioiron in the precipitates was insoluble in detergents and organic solvents and was characterized as mucins. These isolates bound iron in vitro with a Kd of 9.09 x 10(-5). Similar iron binding was observed with commercial mucins. Iron binding to mucin occurred at acid pH and maintained the iron available for absorption with alkalinization. Similar pH-dependent binding to mucin was observed with zinc, cobalt, and lead. Iron competitively inhibited binding of these metals to mucin. However, iron chelates of ascorbate, fructose, and histidine donated iron to mucin at neutral pH. These data provided a role for gastric HCl and intestinal mucin in absorption of iron and metal cations and partial explanation of the competition for absorption between certain metals from the gut lumen. It is postulated that intestinal mucin delivers inorganic iron to intestinal absorptive cells in an acceptable form for absorption.

Haematological adverse effects of histamine H2-receptor antagonists

Histamine H2-receptor antagonists are widely used in the treatment of gastrointestinal diseases related to gastric acid hypersecretion. Cimetidine was introduced into medical practice in 1976 and ranitidine, famotidine and nizatidine in 1981, 1985 and 1987, respectively. Haematological adverse effects are relatively uncommon and most have been reported in cases of cimetidine administration. These adverse effects are reviewed under 4 main headings: (a) blood cytopenias and leucocytosis; (b) coagulation disorders related to drug interactions with oral anticoagulants; (c) reduction of dietary iron absorption; and (d) reduction of dietary cobalamin absorption. 85 reported cases of blood cytopenias attributed to these drugs are reviewed, of which 75 (88%) were associated with cimetidine therapy. In postmarketing surveillance studies, the incidence of cimetidine-associated blood cytopenia has been evaluated at about 2.3 per 100,000 patients. Neutropenia and agranulocytosis are by far the most frequently encountered. Whatever the drug or the type of cytopenia, this adverse effect is almost always rapidly reversible when treatment is stopped. Moreover, in several cases other factors such as underlying diseases or additional drugs could have been responsible, at least partly, for the cytopenia. The pathophysiological basis of these adverse effects remains poorly explained. Various mechanisms have been proposed, which in some cases are probably associated: (a) direct toxicity for haemopoietic stem cells; (b) drug-induced immune reactions leading to blood or bone marrow cell damage, and (c) drug interactions, with increased and prolonged action of potentially haematotoxic drugs. Mechanisms (a) and (c) appear to be of particular clinical importance in cases of impaired renal elimination of H2-receptor antagonists. Cimetidine and probably to a lesser extent ranitidine potentiate the action of oral anticoagulants of both coumarin and indanedione structure. This may result in haemorrhagic complications. Such action is a consequence of the reduced hepatic metabolism of oral anticoagulants through a dose-dependent, reversible inhibition of cytochrome P450. Malabsorption of dietary iron and cobalamin appears to result from inhibition of gastric secretion by the H2-receptor antagonists. This is of no clinical importance in short term treatment, but long term use of H2-receptor antagonists may theoretically contribute to the occurrence of iron or cobalamin deficiency anaemia.

Food iron absorption measured by an extrinsic tag

The paper describes the use of an extrinsic tag of inorganic radioiron to determine the total absorption of nonheme iron from a complete meal. The method was developed by measuring the iron absorbed from vegetable foods containing biosynthetically incorporated (55)Fe (intrinsic tag) and from (59)Fe added as a small dose of inorganic iron to the same meal (extrinsic tag). In studies with maize, black bean, and wheat, a consistent extrinsic: intrinsic radioiron absorption ratio averaging 1.10 was observed. Similar results were obtained with either ferrous or ferric iron as the extrinsic tag, and with doses of the latter ranging from 0.001 to 0.5 mg iron added to a test meal containing 2-4 mg of food iron. Adding the radioiron at different stages in preparation of the test meal also had little effect. Separate administration of the extrinsic tag was less satisfactory when small portions of a single food were employed, but with a complete meal, the separate dose was preferable. The extrinsic tag provided a valid measure of absorption despite marked differences in the iron status of the subject, and with wide changes in absorption imposed by adding desferrioxamine or ascorbic acid to the test meal. These findings indicate that there is a common pool of nonheme iron, the absorption of which is influenced by various blocking or enhancing substances present in the meal.