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

Abstract

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 17β-estradiol (E2). 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), E2 (10-9 M), E2 (10-9 M) plus GH (100 ng/ml), or E2 plus GH and ICI 182-780 at different concentrations. Treatment of hepatocytes with GH or E2 alone did not have any effect on the cellular concentrations of GHBP and GHR. However, the combination of E2 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 E2 for the estrogen receptor (ER), at different concentrations inhibited the E2 and GH-induced stimulation of GHBP and GHR. Furthermore, ER concentrations increased 5- to 7-fold in hepatocytes treated with E2 and GH compared with those in untreated cells or cells treated with either E2 or GH alone. In the present study we have shown that in cultured hepatocytes from virgin female mice, GH or E2 alone did not affect the concentrations of GHBP and GHR. However, E2 and GH together significantly up-regulated GHR and GHBP expression.