Growth hormone (GH) and 17β-estradiol regulation of the expression of mouse GH receptor and GH-binding protein in cultured mouse hepatocytes

In the present study, primary mouse hepatocytes from 8- to 10-week-old virgin female Swiss-Webster mice were perfused with collagenase (100 U/ml) using the two-step method. Isolated hepatocytes were plated in a rat tail type I collagen sandwich configuration to examine the regulation of GH receptor (GHR) and GH-binding protein (GHBP) expression by GH and 17 beta-estradiol (E-2). After 48 h of initial plating, hepatocytes were divided into groups of five replicates and treated for 24 h with medium containing no hormones (controls), GH (100 ng/ml), E-2 (10(-9) M), E-2 (10(-9) M) plus GH (100 ng/ml), or E-2 plus GH and ICT 182-780 at different concentrations. Treatment of hepatocytes with GH or E-2 alone did not have any effect on the cellular concentrations of GHBP and GHR. However, the combination off, and GH up-regulated the cellular concentrations of GHBP and GHR 2- to 3-fold. GHBP and GHR messenger RNA concentrations were also up-regulated 2- to 3-fold. ICI 182-780, a competitive inhibitor of E-2 for the estrogen receptor (ER), at different concentrations inhibited the E-2 and GH-induced stimulation of GHBP and GHR. Furthermore, ER concentrations increased 5- to 7-fold in hepatocytes treated with E-2 and GH compared with those in untreated cells or cells treated with either E-2 or GH alone. In the present study we have shown that in cultured hepatocytes from virgin female mice, GH or E-2 alone did not affect the concentrations of GHBP and GHR. However, E-2 and GH together significantly up-regulated GHR and GHBP expression.