Fig. 4

Signaling pathway in osteoblasts. The top panel shows representative Western blots of actin, ERK1/2^PTyr204, and AKT^PSer473 . The cells from a primary culture were grown both in OSC-supplemented medium (20 μg/ml) over a period of 1, 5, 10, and 15 days as well as in medium supplemented with 100 ng/ml IGF-1 for 1 h. Osteoblasts growing over the period of 15 days without OSC-supplementation served as control (c). The bottom panel summarizes the results of three densitometric measurements of AKT^Ser473 expression (grey column) in relation to the expression level of actin (dotted line). Asterisks indicate significant differences when compared to control (p < 0.001) und hashtags indicate significant differences when compared to day 1 (p < 0.001)