Purification of human intrinsic factor using high-performance ion-exchange chromatography as the final step.

Human intrinsic factor was purified 1430-fold from gastric juice with a yield of 75% using two steps: labile ligand affinity chromatography and high-performance ion-exchange chromatography. Intrinsic factor precipitated in the presence of specific autoantibodies and 15% sodium sulfate, had an estimated Mr of 59 000 in 5% SDS electrophoresis and could bind to the specific ileal receptor in vitro. Its carbohydrate composition could be related to N-lactosaminic and O-glycosidic chains.

The role of sialic acid in the binding of calcium ions to intrinsic factor and its intestinal receptor.

The binding of vitamin B-12-intrinsic factor (cobalamin-intrinsic factor) to its intestinal receptor requires Ca2+. Only low concentrations of Ca were shown to be needed; therefore apparently high-affinity Ca-binding sites, such as neuraminic acids, are involved. Accordingly, the Ca-binding properties of purified human intrinsic factor and purified hog intrinsic factor receptor were studied by gel filtration and by isoelectric focusing.

Tissue distribution of angiotensin converting enzyme in the rat: effect of captopril treatment.

Effect on different tissues with regard to angiotensin converting enzyme during captopril treatment in the rat was studied. Male Wistar-Kyoto rats (n = 9) were treated during four weeks with captopril dissolved into the drinking water at the dose 30 mg/kg/day. Control rats (n = 9) had water only.

Spectral and other studies on the intestinal haem receptor of the pig.

We recently demonstrated the presence of a Triton-solubilized high-affinity haem binder on the pig duodenal brush border membrane. The association of haem to the binding factor was determined using radioactive haem and is now studied by a spectrophotometric technique. The binding alters the Soret absorption band of haem from 395 nm to 413 nm.