A Plasma Glycoprotein Depressed in Vitamin A Deficiency in the Rat: α1-Macroglobulin

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Abstract
Plasma glycoprotein synthesis in normal and vitamin A-deficient rats was investigated by injecting the rats with labeled carbohydrate precursors and then fractionating their plasmas on DEAE-Sephadex. Plasma from deficient rats showed a consistent depression of 30% in the uptake of label into a peak eluting with 0.23 M NaCl. The major component of this peak was identified as the rat α1-macroglobulin, based on its molecular weight (800,000), its mobility on cellulose acetate electrophoresis and its ability to bind trypsin. Although the α1-macroglobulin synthesis appeared to be depressed by 30%, its fractional turnover rate was not affected by vitamin A deficiency (t½ = 18 hours). The trypsin-binding ability of this glycoprotein was used as a comparative measure of its concentration, and the results confirmed that serum levels of this glycoprotein were lower in deficient rats. In severe deficiency, α1-macroglobulin levels dropped to between 10% and 20% of normal levels.

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