B. Freyschuss et al., INDUCTION OF THE ESTROGEN-RECEPTOR BY GROWTH-HORMONE AND GLUCOCORTICOID SUBSTITUTION IN PRIMARY CULTURES OF RAT HEPATOCYTES, Endocrinology, 133(4), 1993, pp. 1548-1554
Hepatic estrogen receptors (ER) mediate estrogenic effects on mammalia
n liver metabolism and are thereby involved in the regulation of impor
tant physiological/pathological processes, such as coagulation, athero
sclerosis, and hypertension. The regulation of the formation of the ER
in primary cultures of rat hepatocytes was studied by assaying ER and
ER mRNA under different endocrine conditions. The ER concentration wa
s measured using two different methods, a ligand-binding technique and
an ER enzyme immunoassay. The results obtained by the two methods sho
wed good correlation, and linear regression analysis gave a correlatio
n coefficient of 0.95. ER concentrations fell to low steady state leve
ls within 16 h after establishing the cell culture and remained low in
the absence of hormonal substitution. Upon medium supplementation wit
h pituitary GH and the glucocorticoid dexamethasone (DEX) in combinati
on, the ER concentration increased 6-fold from 4.2 +/- 1.0 to 25.8 +/-
7.0 fmol/mg cytosolic protein. ER mRNA was measured by solution hybri
dization. Substitution with GH and DEX in combination increased ER mRN
A to 210 +/- 14% of control levels. No effect on ER mRNA stability was
seen after hormone treatment. It is concluded that the regulatory eff
ects of GH and DEX on the hepatic ER in this in vitro system are very
similar to the effects of these hormones under in vivo conditions. The
inducible expression of the ER has never before, to our knowledge, be
en demonstrated in any mammalian liver cell culture system.