The magnitude of the acute phase protein response is attenuated by protein deficiency in rats

We assessed the growth rate and changes in plasma albumin, total protein and alpha 2-macroglobulin concentrations (a major acute phase protein in rats) before and after a subcutaneous injection of turpentine (0.5 mg/kg body wt) in groups of rats receiving one of a series of protein-deficient diets (protein concentrations of 0.5, 1.5, 3.0, 4.5 or 6.0 g/100 g) or a diet containing an adequate level of protein (20 g/100 g) for maximal growth. Increasing protein deficiency in the different groups of animals reduced the basal albumin and total protein concentrations and attenuated the total protein and alpha 2-macroglobulin responses to turpentine. Increasing protein deficiency delayed the time taken for alpha 2-macroglobulin to reach peak concentrations post-injection and its return to basal concentrations. The turpentine-induced hypoalbuminemia was similar in all groups of animals (approximately 10 g/L depression) but restoration to values that were present before turpentine injection was increasingly delayed with increasing protein deficiency. The magnitude of the acute phase response (peak alpha 2-macroglobulin concentration) was found to be directly related to growth rate (r = 0.70, P less than 0.001). We concluded that protein deficiency can alter the pattern and magnitude of the acute phase responses in circulating protein concentrations to an extent that is dependent on the severity of protein deficiency.