The response of the acute-phase plasma protein alpha2-macroglobulin to vitamin A deficiency in the rat.

Alpha2-macroglobulin (alpha2-M) was determined in the sera of vitamin A-deficient and pair-fed control rats. Alpha2-macroglobulin levels were assayed by radial immunodiffusion using a purified standard sample from sera from turpentine-stressed rats. There was no significant increase in the serum level of alpha2-M in vitamin A-deficient rats relative to pair-fed controls, indicating that there was no acute response to the stress of the deficiency. When turpentine was injected to elicit an acute response, the serum level of alpha2-M rose equally (by almost 100-fold) in both deficient and normal rats. It was concluded that the response to vitamin A deficiency of serum glycoprotein synthesis shows some specificity in that the synthesis of alpha2-M in response to stress was not affected by vitamin A, whereas we previously found that levels of alpha1-M, which is very similar to alpha2-M, decline with vitamin A deficiency.