Evidence for an alteration of plasma and liver proteins response to dexamethasone in aging rats

The aim of this study was carried out to analyse the liver and plasma prote ins response to dexamethasone in adult (6-8 months) and old (24 months) rat s in order to ascertain the involvement of glucocorticoids in the aging pro cess. The animals received dexamethasone (Dex) for 5 or 6 days. As Dex decr eased food intake, all groups were pair Fed to dexamethasone-treated old ra ts. The synthesis of mixed plasma and liver proteins (assessed by a floodin g dose of [C-13] valine) was similarly greatly improved in adult and old ra ts after Dex treatment. However. the level of mixed plasma proteins was onl y slightly increased. When specific plasma proteins were assessed, a simila r increase in the concentration of albumin and alpha1 acid glycoprotein was observed in adult and old rats. By contrast, fibrinogen decreased to a gre ater extend in old rats and alpha2 macroglobulin became undetectable in old animals. It was concluded that the response of plasma and liver proteins: to Dex was altered in old rats and may contribute to the pathogenesis of se veral diseases which occur during aging. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.