Purification and characterization of 38-kDa protein in plasma of dietary magnesium-deficient rat.

We have found an increase of a 38-kDa plasma protein level from 10 to 30 days in rats on a magnesium-deficient diet (Mg; 0.001 per cent), using sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This 38-kDa protein returned to the control level after feeding the rats a magnesium-sufficient diet (Mg; 0.07 per cent) for 1 week. Purification of the protein by reverse-phase HPLC separated it into two components (p38k-1 and p38k-2). Amino acid analysis showed that these components were both haptoglobin (Hp) beta-chain. Furthermore, hemoglobin-immobilized affinity chromatography analysis confirmed the increase of Hp in magnesium-deficient rat plasma. This is the first demonstration of an increase of Hp in plasma of dietary magnesium-deficient rats.