Comparative studies on intrinsic factor and cobalophilin in different parts of the gastrointestinal tract of the pig

Marcoullis, George; Merivuori, Hannele; Gräsbeck, Ralph

doi:10.1042/bj1730705f

Cited by 15 publications

(11 citation statements)

References 39 publications

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“…Such an alkaline type of isoprotein does not represent a component of the native R protein (9,35). It most probably corresponds to denatured or partially hydrolyzed protein (9,14,16).…”

Section: Resultsmentioning

confidence: 99%

“…In addition, other concurrent (14) and more recent in vivo studies (17) demonstrated that IF free of Cbl remains biologically, immunologically, and physicochemically unaltered, whereas the R protein(s) are being degraded during normal intraluminal transport. These latter observations supported the thesis (16) that in EPI the R protein(s) are not subject to degradation and therefore the entire fraction of Cbl bound to these nonfunctional proteins will not be absorbed (14,16,17). Recent studies in Rothenberg's laboratory (18) indicated that bile effectively sequesters Cbl from IF to nonfunctional binders and that this process can be reversed after treatment with proteases (18).…”

Section: Introductionmentioning

confidence: 97%

“…in the intestinal lumen can inhibit the ileal absorption of the vitamin, and showed by in vitro studies that purified pancreatic proteases can degrade R proteins but not IF (16). In addition, other concurrent (14) and more recent in vivo studies (17) demonstrated that IF free of Cbl remains biologically, immunologically, and physicochemically unaltered, whereas the R protein(s) are being degraded during normal intraluminal transport. These latter observations supported the thesis (16) that in EPI the R protein(s) are not subject to degradation and therefore the entire fraction of Cbl bound to these nonfunctional proteins will not be absorbed (14,16,17).…”

Section: Introductionmentioning

confidence: 97%

“…The mechanism(s) underlying the pathophysiology of this phenomenon have not been worked out (8)(9)(10)(11)(12). The two principal prerequisites for normal Cbl absorption i.e., the complexing of dietary Cbl to the gastric intrinsic factor (IF) (gastric phase of Cbl transport), as well as the subsequent attachment of the latter complex to specific receptors located on the ileal enterocyte (ileal wall phase) (13)(14)(15), have not been found to be directly related to parameters of the exocrine pancreatic function. Consequently the malabsorption of Cbl in EPI may not be considered in terms of events occurring during the gastric and ileal wall phase of Cbl transport.…”

Section: Introductionmentioning

confidence: 99%

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Cobalamin malabsorption due to nondegradation of R proteins in the human intestine. Inhibited cobalamin absorption in exocrine pancreatic dysfunction.

Marcoullis¹,

Parmentier²,

Nicolas³

et al. 1980

J. Clin. Invest.

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A B S T R A C T In vivo studies demonstrate that the pancreatic enzymes and the ionic environment in the upper gastrointestinal tract are essential determining factors for transport and absorption of cobalamin in man.Jejunal fluid was aspirated from healthy human volunteers after administration of cyano[57Co]cobalamin preparations. Immunochemical analysis of the aspirates demonstrated that all isotopic vitamin was transferred to a protein that is identical to the gastric intrinsic factor in terms of molecular mass (57,500), ionic nature (mean pI, 5.09), and reactivity with antiintrinsic factor sera. However, in the aspirates from patients with exocrine pancreatic dysfunction the vitamin was found to be coupled >60% to a protein identical to R proteins in terms of molecular mass (125,000), ionic nature (mean pI, 3.51), and reactivity with anti-R protein and anti-intrinsic factor sera. The preferential transfer of cobalamin to R proteins in the patients and to intrinsic factor in healthy subjects was associated, respectively, with low and normal levels ofpancreatic enzymes in the intestine and these in turn were paralleled respectively by impaired and normal ileal absorption of cobalamin. These findings confirm the suggestion that the formation of unabsorbable cobalamin complexes may be the reason of impaired vitamin absorption in exocrine pancreatic insufficiency.This paper was presented in part at the 3rd European Symposium on Vitamin B12 and Intrinsic Factor, March 1979, Zurich, Switzerland.Dr. Marcoullis is a visiting professor of medicine under the auspices of Institut National de la Sante et de la Recherch6 Medicale at the University of Nancy. The permanent address for Dr. Marcoullis and Ms. Jimenez is Department of Medicine, Veterans Administration Hospital, Brooklyn, N. Y. Received for publication 2 November 1979 and in revised form 19 May 1980. 430 Observations made with other selected patients demonstrate: (a) that decreased enzyme activity and nondegradation of R proteins may also be due to nonactivation ofpancreatic zymogens in an acidic pH ofthe intestinal juice and; (b) that in the absence of an acidic environment in gastric juice the vitamin transported to the jejunum couples to intrinsic factor when pancreatic function is normal, and to intrinsic factor and R protein in exocrine pancreatic insufficiency. The observations made with these selected patients may explain why not all patients with exocrine pancreatic insufficiency develop impaired cobalamin absorption, and also why the malabsorption is corrected by the administration of bicarbonate in certain patients. INTRODUCTIONA common feature of the untreated exocrine pancreatic insufficiency (EPI)l is the impaired ileal absorption of cobalamin (Cbl; vitamin B,2) (1-8). The mechanism(s) underlying the pathophysiology of this phenomenon have not been worked out (8-12). The two principal prerequisites for normal Cbl absorption i.e., the complexing of dietary Cbl to the gastric intrinsic factor (IF) (gastric phase of Cbl transport), as well as th...

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“…Such an alkaline type of isoprotein does not represent a component of the native R protein (9,35). It most probably corresponds to denatured or partially hydrolyzed protein (9,14,16).…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Cobalamin malabsorption due to nondegradation of R proteins in the human intestine. Inhibited cobalamin absorption in exocrine pancreatic dysfunction.

Marcoullis¹,

Parmentier²,

Nicolas³

et al. 1980

J. Clin. Invest.

View full text Add to dashboard Cite

show abstract

“…Sera were prepared from blood collected from pernicious anemia patients having circulating anti-IF antibodies. Rabbit anti-human R-binder (anti-R-binder) sera were produced using granulocyte preparations as antigen (10). Specific IF-receptor was solubilized from fresh porcine ileal mucosal scrapings as described (10).…”

mentioning

confidence: 99%

The Intraluminal Transport of Vitamin B12 and the Exocrine Pancreatic Insufficiency

Parmentier

Marcoullis

Nicolas

1979

Experimental Biology and Medicine

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Resorption von wasserlöslichen Vitaminen

Rehner¹

1983

Dünndarm A

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Comparative studies on intrinsic factor and cobalophilin in different parts of the gastrointestinal tract of the pig

Cited by 15 publications

References 39 publications

Cobalamin malabsorption due to nondegradation of R proteins in the human intestine. Inhibited cobalamin absorption in exocrine pancreatic dysfunction.

Cobalamin malabsorption due to nondegradation of R proteins in the human intestine. Inhibited cobalamin absorption in exocrine pancreatic dysfunction.

The Intraluminal Transport of Vitamin B12 and the Exocrine Pancreatic Insufficiency

Resorption von wasserlöslichen Vitaminen

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