Independent effects of protein and energy deficiency on acute-phase protein response in rats

The effect of restricting either protein intake alone or all dietary constituents on the acute-phase protein response was assessed during a 3-wk period after a standardized "injury" (i.e., subcutaneous injection of turpentine 0.5 ml/kg body wt) to rats. Sequential measurements were made of the circulating concentrations of alpha 2-macroglobulin (alpha 2-M), albumin, and total protein. Results were compared with those obtained from normally fed rats that were also injected with turpentine and with saline-injected rats (controls) receiving each dietary regimen. Turpentine-treated rats showed a decrease in albumin concentration by approximately 10 g/L within 2-4 days. In the protein-deficient rats, recovery to preinjection levels had not occurred by 3 wk, but in the other groups, it was complete by 7-9 days. The protein-deficient animals also showed an attenuated response in alpha 2-M and total protein and delay in their recovery toward normal. Maximal alpha 2-M and total-protein responses in this group of animals was only 44 and 39%, respectively, of those found in the control group. We conclude that protein deficiency attenuates the magnitude and alters the time profile of the positive (alpha 2-M and total protein) and negative (albumin) acute-phase protein responses to injury, independent of the severity of the stimulus.