Central and peripheral actions of somatostatin on the growth hormone–IGF-I axis
J. Clin. Invest. Robert D. Murray, et al. 114:349 doi:10.1172/JCI19933 [Go to this article.]

Figure 7
SRIF suppression of STAT5b. (A) PTP activity was measured in primary hepatocytes treated with vehicle (Control), GH (500 ng/ml), and coincubations of GH with 100 nM SRIF or octreotide. PTP activity was assessed by incubation of cell lysates with tyrosine phosphopeptides and the phosphate production measured using a molybdate dye. *P < 0.05. (B) STAT5b was immunoprecipitated from whole-cell lysates of primary hepatocytes treated with vehicle, GH (500 ng/ml), and cotreatments of GH and 100 nM SRIF for 20 minutes. Immunoprecipitates were subject to polyacrylamide gel electrophoresis and membranes blotted for phospho-STAT5b (upper panel) and, after stripping, for STAT5b (lower panel). Phosphorylated STAT5b (pSTAT5b)/STAT5b was visible as a 92-kDa band; a second band that migrated more slowly was visible at approximately 96 kDa and likely represents serine phosphorylated STAT5b (arrows). (C) STAT5b was immunoprecipitated from hepatocyte nuclear extracts treated with GH (500 ng/ml) or cotreated with GH and 100 nM SRIF. Following electrophoresis, membranes were probed for STAT5b. The lower arrow corresponds to the heavy chain of the IgG used in the immunoprecipitation.