[Age-related characteristics of corticosteroid interactions with blood transport proteins]

In blood of old rats the content of corticosteroid transport proteins was decreased, as a result of which their balance was distorted and negative cooperativity between transcortin-binding sites developed. Values of Hill coefficient were below 1 in the hormone-protein interactions, which appears to occur due to polymerization of the protein or to appearance of unknown factors(s) in blood of old animals. After treatment of the old rats blood serum with activated charcoal the steroid-binding transcortin capacity and its affinity to hormone was increased and the negative cooperativity was not observed.