Corticosteroid-binding globulin synthesis and distribution in rat white adipose tissue.

Corticosterone binding (CB) capacity was determined in visceral and subcutaneous white adipose tissue (WAT), as well as in plasma of lean Zucker rats. Perfusion of rats with saline eliminated most liver and kidney corticosterone binding but did not affect CB in WAT. The cytosol extracts of isolated cells, however, did not bind corticosterone in detectable amounts. By means of a RT-PCR procedure it was found that corticosterone-binding globulin (CBG) was expressed in WAT. By immunohistochemical detection in WAT sections, CBG was seen in a thin layer surrounding the cells near the plasma membrane. These data suggest that the CBG layer surrounding the cells may act as a protective barrier limiting the access of glucocorticoids to adipocytes.