Studies by Quantitative Immunoelectrophoresis on Iron Binding Proteins in Haemochromatosis

Abstract

1. The concentrations of a number of plasma proteins in patients with haemochromatosis were determined by quantitative immunoelectrophoresis, particular attention being paid to the three iron transporting proteins.2. Transferrin and haptoglobin were within normal limits; haemopexin was significantly greater than normal (P< 0.001).3. Other changes observed were a significant (P<O.OOl) increase of a1 antitrypsin, of a, macroglobulin and PlA-,-; these changes are discussed.At least three serum proteins are involved in the ordinary physiological transport of iron. These are, first, transferrin, which carries free iron. In normal circumstances transferrin is only partly saturated, whereas in haemochromatosis it may be 90400% saturated. Second, haptoglobin; this binds haemoglobin, and although it is, known that the mass of haptoglobin catabolized per day is not enough to play a large role in the daily haemoglobin breakdown, it is conceivable that an upset in this mechanism could, over the years, account for an increase in the deposition of iron. And finally, haemopexin transports iron in the form of haem. Very little is known about the metabolism of this protein. It is thought (Miiller Eberhard eta1.,,1969) that haemopexin is a 'suicidal' protein like haptoglobin, in other words, after haem has combined with haemopexin the two are catabolized together. There is some evidence to support this hypothesis, in that a low haemopexin is sometimes found in haemolytic conditions ; however, the concentration of haemopexin seldom drops as low as is found for haptoglobin. For these reasons it seemed of importance to study the concentrations of these proteins in primary idiopathic haemochromatosis, a condition associated with a slow accumulation of iron in the tissues and eventual portal cirrhosis, and to compare the concentrations found with those in the normal population. At the same time the concentration of eight other pr'oteins were studied.

Serum protein levels in primary biliary cirrhosis

“…A significant increase in this protein has previously been reported in patients with haemochromatosis (Amin, Clarke, Freeman, Murray-Lyon, Smith, and Williams, 1970), and in the discussion of their results these authors predicted that in other diseases with primary liver damage similar high concentrations would be found. The present study supports their surmise, but does not indicate whether the elevated serum levels reflect increased synthesis or decreased catabolism.…”

“…The physiological role of %2-macroglobulin has not been defined and so the significance of the observed increase in serum levels in primary liver disease is obscure. Amin et al (1970) found a significant increase in fl1C/P1A levels in their patients with haemochromatosis. More recently Fox, Dudley, and Sherlock (1971) found normal concentrations of P,C/P1A in the majority of 150 patients with chronic liver disease, and in particular, normal levels were found in 30 patients with primary biliary cirrhosis, an observation consistent with our present results.…”

Serum Protein Changes after Injury

“…Since it is difficult to obtain pure standards for many individual proteins, use has been made of a pooled serum sample as the reference material, and results are expressed as 'per cent of reference serum'. Although this pool was obtained from normal blood donors, no claim is made that it represents normal values; the latter have already been defined by studying individual subjects relative to this standard pool (Clarke & Freeman, 1968). A single pool of antiserum made in goats, by using complete Freund's adjuvant, was used throughout this study.…”

“…Since at least forty individual serum proteins may be determined by this technique, the problem of identification is considerable. In the present study fifteen proteins have been identified by name, and a further five by numbers (Freeman & Smith, 1970). The nomenclature is given in Table 1.…”

Sites of Formation of the Serum Proteins Transferrin and Hemopexin

“…Growing interest in the heme-binding serum protein hemopexin has recently developed in response to the observation that its concentration changes from the normal in a variety of diseases. A fall, reciprocal to plasma heme levels, is encountered in hemolysis (1)(2)(3) and in certain porphyrias (4 and our unpublished observations), and a rise in hemochromatosis (5), diabetes mellitus (6), and malignancies (7). Clinical Received for publication 20 June 1972 and in revised form 25 October 1972. in iron deficiency and the decrease in inflammatory reactions (8).…”