Insulin-like growth factor-1 does not affect sphingosine kinase-1 or sphingosine kinase-2 protein content. C2C12 myoblasts were incubated with DMEM containing 1 mg/ml bovine serum albumin (BSA) for the indicated time intervals in the absence (−) or in the presence (+) of 50 ng/ml insulin-like growth factor-1 (IGF-1). Top, aliquots of total cell lysates were used to perform Western analysis, using specific anti-sphingosine kinase (SK)1 and anti-SK2 antibodies. A representative blot is shown. Bottom, densitometric analysis of at least three independent experiments. Data are the mean ± SEM and are reported as protein expression normalized to β-actin, -fold change over control (set as 1).