Sex hormone binding globulin expression and colocalization with estrogen receptor in the human Fallopian tube

The detection of sex hormone binding globulin (SHBG) or SHBG mRNA in severa l sex steroid target tissues, has raised the possibility that SHBG modulate s the action of sex steroids outside the vascular compartment. The presence of SHBG mRNA was investigated by RT-PCR in the poly (A(+)) RNA fraction of the human Fallopian tube. Human and rat liver were used as positive and ne gative control tissues, respectively. The electrophoretic analysis of the a mplified PCR products showed bands at 219 bp, corresponding to the expected size of the SHBG cDNA, in the Fallopian tube and human liver but not in ra t liver, indicating that SHBG might be sinthezised by the Fallopian tube. T he cellular localization of SHBG and of estrogen receptor (ER) was examined by immunohystochemistry in consecutive sections of Fallopian tube tissues for individual staining or double immunostaining in the same section. Speci fic immunostaining of SHBG was present in the epithelial, vascular and musc le cells of the ampullary and isthmic region. In epithelial cells, immunore active SHBG was present in the apical end with the highest concentration cl ose to the luminal membrane. The ER was localized in the nuclei of epitheli al, stromal and muscle cells of the ampulla and isthmus. Double immunostain ing showed that SHBG and ER are colocalized principally in epithelial cells of the ampulla and in muscle cells of the isthmus. In conclusion, the dete ction of SHBG and SHBG mRNA and the localization of SHBG in estrogen target cells was shown. These findings support the hypothesis that SHBG might reg ulate sex steroid action at the tissue level. (C) 1999 Published by Elsevie r Science Ltd. All rights reserved.