CORTICOSTEROID-BINDING GLOBULIN MESSENGER-RNA LEVELS IN HUMAN UTERINEENDOMETRIUM

Corticosteroid-binding globulin (CBG or transcortin) is a specific pla sma glycoprotein, which binds steroid hormones (cortisol, corticostero ne, and progesterone), and plays a role in transporting these steroids , altering their concentrations in blood, and influencing their biolog ical actions. CBG has been previously shown to be synthesized in the l iver, but recently it has been reported that immunoreactive CBG is loc alized in target tissues. In the present work, CBG mRNA was detected i n normal human endometrial tissues by Northern blot analysis and rever se transcription-polymerase chain reaction. Its level was higher (P < 0.05) in the secretory phase than in the proliferative phase. In the s ecretory phase, the endometrial CBG mRNA level was negatively correlat ed with the serum progesterone level (P < 0.01). While there was no po sitive correlation between the levels of endometrial CBG mRNA and seru m estradiol (E2), there was a positive correlation between the endomet rial CBG mRNA level and the serum E2/progesterone ratio (P < 0.05). Th ese findings suggest that CBG is synthesized in the uterine endometriu m, predominantly in the secretory phase, and that the serum E2/progest erone ratio exerts an influence on the synthesis of intercellular CBG.