Injection of JAK2/STAT5 inhibitor abolished the promotive effect of Pro-Gly on IGF-1 expression and secretion in mice. Twenty-eight 6-week old female mice were randomly divided into 4 groups ( n = 7). (A) Western blot analysis of phospho-JAK2 (p-JAK2), JAK2, phospho-STAT5 (p-STAT5), STAT5 and prepro IGF-1 in mice liver after injection. β-actin was used as loading control. The mice were intraperitoneal injected with physiological saline (Control), Pro-Gly (100 mg/kg, 1 h), JAK2 inhibitor AZD1480 (30 mg/kg, 3 h) or Pro-Gly+AZD1480 in a volume of 100 μL, respectively. (B) Mean ± SEM of immunoblotting bands of prepro IGF-1, p-JAK2/JAK2, and p-STAT5/STAT5 ( n = 7). The intensities of the bands were expressed as the arbitrary units. (C) IGF-1 mRNA level in mice liver ( n = 7). (D) Serum levels of IGF-1 ( n = 7). Bars that do not share the same letter are significantly different ( P