Effect of burn injury on corticosteroid-binding globulin levels in plasma and wound fluid

Corticosteroids exert inhibitory effects on wound healing. They circulate, largely bound to corticosteroid-binding globulin, and the plasma concentrations of this protein determine their bioavailability. The amount of corticosteroid-binding globulin in wounds and the related effects of burn injury are not known. We have therefore measured corticosteroid-binding globulin in serum and wound fluid obtained from subcutaneously implanted sponges, retrieved 1, 3, and 10 days after insertion in rats. The effect of burning was studied by comparing rats that had a small scald burn with sham-burned control rats. In serum, corticosteroid-binding globulin levels were lower in burned rats than in control animals: the difference was 22%, 28%, and 37% for days 1, 3, and 10, respectively (p < 0.05 for each comparison), and values at day 1 were lower than at days 3 and 10 in control rats (p < 0.05) but not in burned rats. In wound fluid, corticosteroid-binding globulin levels were lower in burned rats than in control animals: the difference was 23%, 24%, and 34% for days 1, 3, and 10, respectively (p < 0.01 for all comparisons), and the values were significantly higher (p < 0.05) at day 1 when compared with values at day 10 in both groups. We therefore conclude that a small burn injury has significant effects on levels of corticosteroid-binding globulin on serum and wound fluid corticosteroid-binding globulin. The decreased concentration of wound fluid corticosteroid-binding globulin at day 10 versus day 1, with a concomitant increase in serum corticosteroid-binding globulin, suggests an accelerated degradation of the protein within the wound; this phenomenon is exaggerated by the burn injury. This is supported by Western blot analysis, which revealed the appearance of a small polypeptide that reacts with an antiserum against rat corticosteroid-binding globulin in wound fluid at day 10.