EFFECT OF OLEOYL-ESTRONE ADMINISTRATION ON CORTICOSTERONE BINDING TO TISSUES OF LEAN AND OBESE ZUCKER RATS

A group of female Zucker lean and obese rats was treated with 3.5 mu m ol/day kg of oleoyl-estrone in liposomes (OE) injected i.v. continuous ly for 14 days with inserted osmotic minipumps. Samples of liver were extracted on days 0, 3, 6, 10 and 14 and the expression of corticoster one-binding globulin (CBG) was determined by Northern blot. On the sam e dates, the total binding capacity of plasma, liver, periovaric white adipose tissue (WAT) and subcutaneous WAT was also determined using t ritium-labelled corticosterone. Treatment with OE resulted in diminish ed CBG gene expression in the liver, this being more marked in the obe se rats. Basal (time 0) corticosterone binding was higher in the plasm a, liver and WAT of lean rats. Treatment with OE resulted in a gradual and general loss of binding capacity in the plasma and all tissues st udied, for lean and obese rats alike. Since CBG decreases may result i n enhanced glucocorticoid availability (and effects), the global decre ase in corticosterone binding observed can be interpreted as a counter active response to the energy imbalance elicited by OE. (C) 1998 Elsev ier Science Ltd. All rights reserved.