Radioactive Vitamin B12 Research Articles

A family study of pernicious anaemia. II. Intrinsic factor secretion, vitamin B12 absorption and genetic aspects of gastric autoimmunity.

Summary A good but not absolute correlation between the presence of the gastric parietal cell antibody and impairment of gastric secretion was observed in the relatives of patients with pernicious anaemia. By analogy, although the majority of relatives without the antibody secreted normal amounts of acid and of intrinsic factor nearly one‐fifth secreted unexpectedly small amounts of intrinsic factor.There was a highly significant correlation between the amounts of acid and of intrinsic factor secreted in response to histamine or gastrin and as a rule impairment of secretion affected these substances to the same extent. However, one young relative who did not have gastric or thyroid antibodies was considered to have selective impairment of intrinsic factor secretion.Thirty‐eight subjects had direct measurements of intrinsic factor and tests of vitamin B12 absorption. Twenty‐seven of these secreted less than 600 units of intrinsic factor in the hour following stimulation and all but two had malabsorption of radioactive vitamin B12. Similarly all but two of the 11 subjects who secreted more than this amount had normal absorption of the vitamin.Twenty‐two per cent of the probands of the study had a family history of pernicious anaemia, 18 per cent one of thyroid disease, 20 per cent one of diabetes mellitus and 3.8 per cent had a family history of carcinoma of the stomach.Analysis of the distribution of inherited characteristics showed that there was a slight but not significant excess of blood group A in the patients with pernicious anaemia and that the proportion of patients with Lea‐positive red cells was lower than the figure quoted for the general population. Neither in the probands nor in their relatives was there an association between blood group A or the Lea group and the tendency to form circulating antibodies to gastric parietal cells. Moreover, although the proportion of patients with pernicious anaemia who had light‐coloured eyes was of the same order as in a previous study from this department, the prevalence of gastric parietal cell antibodies was no higher in such patients than in those with dark eyes, nor was the prevalence of the antibodies significantly increased in patients who gave a history of premature greying.The gastric parietal cell antibody was no more common in the spouses of probands than in matched control subjects. It was further equally common in relatives of probands without the antibody as in relatives of probands with the antibody. Analysis of three families in which both parents had pernicious anaemia and of seven families in which it was possible to study both parents of the proband suggested that the inheritance of the tendency to form gastric parietal cell antibodies was not a simple one. It appeared that the varying patterns of distribution of the antibody in these families could be best explained by suggesting that the tendency to form the antibody is inherited as a dominant characteristic with an incomplete degree of penetrance.

Congenital Pernicious Anemia with Coexistent Transitory Intestinal Malabsorption of Vitamin B12

Abstract Pernicious anemia with coexistent transitory intestinal malabsorption of vitamin B12 has been established in adults. In this report a child with congenital pernicious anemia was documented to have had transitory selective intestinal malabsorption of vitamin B12. The diagnosis of congenital pernicious anemia was established by the age of the patient, absence of intrinsic factor in gastric fluid, lack of antibodies to intrinsic factor and parietal cells, presence of HCl in gastric fluid, and normal gastric biopsy. The xylose excretion test, 72-hour fecal fat determination, upper gastrointestinal series, and biopsy of the jejunum were normal, but the Schilling test was abnormal with hog intrinsic factor of known potency on two occasions, indicating selective malabsorption of vitamin B12. Seven months after therapy the Schilling test was still abnormal without intrinsic factor, but was normal with both human and hog intrinsic factor. The normal absorption with intrinsic factor after therapy is indicative that the selective malabsorption which was originally present was probably a consequence of the vitamin B12 deficiency resulting from lack of intrinsic factor. In patients with abnormal radioactive vitamin B12 absorption tests with administration of intrinsic factor, coexistent pernicious anemia must be excluded by demonstration of intrinsic factor in gastric fluid.

Plasma turnover of 57cobalt-vitamin B12 bound to transcobalamin I and II.

The plasma turnover of radioactive vitamin B12 bound in vitro to each of the two plasma binders (transcobalamins) was studied after intravenous injection. The observed T 1/2 values for the radioactive B12 were 9–10 days when bound to transcobalamin I and about 1.5 hours when bound to transcobalamin II. In both cases, the plasma curves yielded similar final slopes, corresponding to T 1/2 values of 9.3 and 9.8 days. In the study with transcobalamin II, this is shown to be due to rapid reappearance in the plasma of the radiocobalt label bound to transcobalamin I.

Co57 Vitamin B12 Clearance Studies in Pernicious Anaemia

Clearance rate of intravenously administered radioactive vitamin B12 in untreated pernicious anaemia patients is slow in 50 per cent of cases studied. Administration of labelled vitamin B12 bound to slow serum to ‘normal clearing’ pernicious anaemia subjects or to normal persons is followed by normal clearance rate. Radioactive vitamin B12 bound to normal serum is cleared at a normal rate in pernicious anaemia patients with slow clearance rate. Radioactive vitamin B12 bound to slow serum when mixed with normal serum in proportions of 1:1 or 1:0.5 is cleared at a normal rate in ‘slow clearing’ pernicious anaemia patients. These studies suggest the presence of a ‘serum factor’ in normal serum and some patients with pernicious anaemia in relapse which enhances clearance of vitamin B12 bound to ‘slow serum’.

54 Congenital Pernicious Anemia with Coexistent Transitory Intestinal Malabsorption of Vitamin B12

Pernicious anemia (PA) with coexistent transitory intestinal malabsorption of vitamin B12 has been documented in adults. This report is the first description of proven transitory selective intestinal malabsorption of vitamin B12 in congenital PA. A vitamin B12 responsive anemia was demonstrated in the patient, a 2 ½-year-old girl, by change in the bone marrow from megaloblastic hyperplasia to normoblastic hyperplasia 48 h after 5 μg of vitamin B12. No intrinsic factor (IF) was found in gastric fluid by in vitro assay before and again 4 and 6 weeks after therapy. Congenital PA was established by the age of the patient, absence of IF in gastric fluid, lack of antibodies to IF and parietal cells, presence of HCl in gastric fluid, and normal gastric biopsy. The xylose tolerance test, 72 h fecal fat determination, upper GI series, and biopsy of the jejunum were normal, but the Schilling test was abnormal with hog IF of known potency on two occasions, indicating selective malabsorption of vitamin B12. Six months after therapy the Schilling test was still abnormal without IF, but was normal with both human and hog IF. This normal absorption with IF after therapy is indicative that selective malabsorption was originally present, probably as a consequence of the vitamin B12 deficiency resulting from IF lack. In patients with abnormal radioactive vitamin B12 absorption tests with administration of IF, coexistent PA must be excluded by demonstration of IF in gastric fluid. (SPR)

Abnormally increased glomerular filtration rate in short-term insulin-treated diabetic subjects.

Functional changes in the microvascular system appear to precede the morphological changes in the conjunctiva and retina of young subjects with diabetes mellitus. Similar functional changes might occur in the renal microvascular system and hemodynamics and possibly lead to a disturbance in the glomerular filtration rate. A preliminary study of the glomerular filtration rate (GFR) using the radioactive vitamin B12 method in young, insulin-treated patients with short duration of diabetes is reported. The average GFR in eighteen diabetic subjects was 137.8 ml. per min. per 1.73m2 with a standard deviation of 24.3 ml. in contrast to the average GFR in twelve control subjects which was 102.9 ml. with a standard deviation of 15.1 ml. This difference in GFR is highly significant. The reasons for the increased GFR in diabetics with short duration of their disease are discussed.

Preferential in vitro Binding of Radioactive Vitamin B12 by an Abnormal Serum Protein in Chronic Myeloid Leukaemia

ALTHOUGH considerable work has been done in the past decade on in vivo and in vitro binding of vitamin B12 (refs. 1–4), the precise mechanisms of binding and the physiological significance of the binding patterns obtained remain uncertain.

Tubeless gastric analysis as a tool to measure gastric secretory activity.

SummaryThis report discusses the tubeless techniques available to evaluate the capability of the gastric mucosa to secrete acid, pepsinogens, and intrinsic factor. The presence of gastric acid can be determined by proper application of the azure A ion‐exchange resin technique. Pepsinogen and intrinsic factor activity may be inferred from measurement of the urinary pepsinogens and the absorption of an oral dose of radioactive vitamin B12 with or without added intrinsic factor, respectively. A normal serum vitamin B12 level may be present in a patient with a recent failure of intrinsic factor secretion: however, a decreased level is suggestive of the absence of intrinsic factor in individuals who have no evidence for malabsorption. The value of the rapid charcoal method developed in Herbert's laboratory for measuring serum vitamin B12 is discussed.The results of the tubeless tests have clinical significance in the diagnosis of gastritis and vitamin B12 deficiency, in the management of a patient with a gastric ulcer niche, and in suggesting further studies for early detection of gastric malignancy.

Inulin, 57Co-labelled vitamin B12 and endogenous creatinine clearances in the measurement of glomerular filtration rate in man.

SUMMARY In 14 cases, simultaneous clearances of inulin (range 39 to 160 ml. per minute) and endogenous creatinine were measured, and in 11 of these cases, the results were compared with the simultaneous clearance of radioactive (57Co) vitamin B12. The clearance of free (dialysable) 57Co vitamin B12 correlates closely with inulin clearance (ρ=0·985), and can be used as a measure of glomerular filtration rate. [Clearance of vitamin B12 (free)=1·07 clearance of inulin—10·9±5·48 (2 S.D.). ] The protein bound (non‐dialysable) fraction of the plasma 57Co vitamin B12 varied from patient to patient, and in the same patient at different times (range, 9·6% to 35·7%; mean, 17·7% of total), in spite of presaturation with stable vitamin B12. Because of this, the clearance of vitamin B12 is a valid measure of glomerular filtration rate only when correction is made for plasma protein binding as measured in the individual subject. The correlation between inulin and endogenous creatinine clearance was less precise. [Ratio of clearance of creatinine to clearance inulin=1·20±0·38 (2 S.D.).]

Long-term observation of gastrectomized rats with regard to development of vitamin B12 deficiency.

The glandular portion of the stomach was removed in rats. The animals were given an excess of iron orally, and survived for 16–26 months in a good nutritional condition. Despite of impaired ability to absorb radioactive vitamin B12 and reduced levels of vitamin B12 in the serum and liver, the animals did not develop megaloblastic anaemia.Possible reasons for the absence of anaemia are discussed. The vitamin B12 activity was more reduced in the liver than in the serum, suggesting that the liver depots were mobilized to maintain the serum level. The folic acid activity in the liver was not significantly reduced following the operation.

RELEASING FACTOR AND ENDOGENOUS VITAMIN B12.

SummaryExperiments were performed for the purpose of grossly identifying the substance responsible for the release, by rat intestinal segment extracts and human organ extracts, of vitamin B12 bound to rat stomach extract or normal human gastric juice. It has been found that the active principle in the proximal area and mid-ileum of the rat small intestine is dialyzable and that its distribution parallels closely that of endogenous vitamin B12. Non-radioactive vitamin B12 has been found to be very active in the release of radioactive vitamin B12 bound to rat or human intrinsic factor concentrate. This appears to be due to its ability to equilibrate with the bound form. In a complex equilibrium system, endogenous vitamin B12 appears to account for substantially all of the activity displayed by the proximal area and mid-ileum of the rat small intestine, and by mucosa homogenates from beef small intestine and various human organ extracts. Vitamin B12 bound to hog intrinsic factor on the other hand shows littl...

Gastrointestinal Absorption, Plasma Transport, Surface Distribution, and Urinary and Fecal Excretion of Radioactive Vitamin B12 in Iron Deficiency

Abstract No evidence of vitamin B12 deficiency or of any mechanism which might lead to vitamin B12 deficiency, such as defective absorption or increased urinary or fecal excretion of the vitamin, has been found in iron-deficient subjects in whom gastric acid secretion and gastric biopsies were normal. It is concluded that when vitamin B12 deficiency occurs in iron-deficient subjects it is the result of gastric atrophy. An unexplained finding was delayed disappearance of an intravenous dose of Co58-B12 from the plasma in iron-deficient subjects.

INTESTINAL DISTRIBUTION OF INTRINSIC FACTOR AND VITAMIN B12 ABSORPTION.

Evidence is presented that intrinsic-factor (IF) activity is present in the small intestine as far down as the ileal end. Physiologic doses of radioactive vitamin B12 without IF were applied directly into various levels of the intestine by surgical and other means in man and rats, and significant absorption was obtained from the small intestine. Absorption inhibition by ethylenediaminetetraacetate and its counteraction by Ca ion demonstrated that such absorption was dependent on IF action. The large intestine was shown to be incapable of physiologic absorption of vitamin B12, and IF was totally ineffective. It is proposed that physiologically, gastric IF descends with some activity in the small intestine, where more of the food vitamin B12 is liberated by digestion and subjected to IF.

The absorption of radioactive vitamin B12 and the secretion of hydrochloric acid in patients with atrophic gastritis

The absorption of radioactive vitamin B12 and the secretion of hydrochloric acid in patients with atrophic gastritis

Biological half-life of vitamin B12 in plasma.

BY kinetic analysis of isotope experiments using tracer doses of radioactive vitamin B12, Reizenstein1 has deduced that the biological half-life of vitamin B12 in the plasma is about 6 days. Confirmation of this finding has been obtained by a different approach. Working with injected doses of radioactive vitamin B12 in the range 50–1,000 µg, a linear relationship with a coefficient of correlation differing significantly from zero was found between the logarithm of the amount of injected vitamin B12 retained in the body and the time in days for the serum vitamin B12 level to fall to the pre-injection level, the lower limit of normal, in patients with pernicious anaemia2. The regression equation was Y= 17.0886x − 0.4270 when Y = the time in days and x = the logarithm of the retained dose. From this information it can be calculated that the biological half-life in the plasma of the radioactive vitamin B12 retained in the body was 5.14 days and that the velocity constant (k) is 0.1347 days−1. The closeness of the estimates is satisfying particularly as they were obtained by totally different experimental methods. The short biological half-life in plasma contrasts sharply with that in the liver, which has been calculated to average about 12 months.

The reliability and reproducibility of the Schilling test in primary malabsorptive disease and after partial gastrectomy

A study of the reproducibility and reliability of the Schilling test in patients with primary malabsorptive disease and after partial gastrectomy is reported. The value of the test was assessed...

The differential diagnosis of megaloblastic anaemia.

SUMMARYIn a series of 179 adult patients with megaloblastic anæmia there were 95 cases of pernicious anæmia and 38 cases of nutritional megaloblastic anæmia. These two conditions were difficult to distinguish clinically in many instances, especially if the patient was elderly and did not have an obviously faulty diet. The estimation of serum vitamin B12 concentration and radioactive vitamin B12 absorption tests were valuable in differential diagnosis ; but there was some overlap in results in the two groups, and these tests need interpretation in the light of other clinical and laboratory findings.Fourteen patients suffered from post‐gastrectomy megaloblastic anæmia. In five, the mechanism appeared to be lack of intrinsic factor secretion, in five, nutritional deficiency of folic acid, and in four, intestinal malabsorption.

Megaloblastic anemia; an important clue to precise diagnosis.

In North America, most patients who have megaloblastic anemia will be found to have pernicious anemia. Usually, diagnosis of conditions in which megaloblastic anemia is a feature is not difficult, but when problems arise there are special technics available to help resolve them. Measurement of serum levels of vitamin B12, the Schilling test using radioactive vitamin B12 both alone and with added intrinsic factor, plus the history, physical findings and other appropriate tests make it possible to reach a precise diagnosis. When similar methods are evolved for studying folic acid, the total picture of megaloblastic anemias should be comparatively clear.

The Plasma Disappearance of Radioactive Vitamin B12in Myeloproliferative Diseases and Other Blood Disorders

Abstract 1. The plasma disappearance of a small intravenous dose of radioactive vitamin B12 was determined in control subjects and in patients with various blood disorders. 2. A delayed, sometimes irregular, disappearance was observed in the majority of patients with acute and chronic myelogenous leukemia, myeloid metaplasia, and polycythemia vera. 3. Disappearance was normal in the lymphogenous leukemias, secondary polycythemia and relative polycythemia. 4. The abnormalities observed are believed to indicate an abnormality of vitamin B12 metabolism common to the diseases of the myeloproliferative group and are further evidence of the close relationship between these diseases.

Metabolites of Vitamin B12 in Bile after Parenteral Administration of the Vitamin

SEVERAL investigations have shown that, in animals and in man1, the major proportion of the total radioactivity excreted after an injection of radioactive vitamin B12 is excreted in the bile, and that in man at least two-thirds of the biliary radioactivity is re-absorbed from the intestine. This indicates that vitamin B12 is subject to an entero-hepatic circulation similar to other substances in bile.