FGF21 Activates Preferentially Adipose FGFR1-KLB Figure 8. Differential tissue-specific responses to FGF21 and FGF19 as measured by the activation level of Erk1/2. Endocrine FGF treatment and tissue collection in mice were as described in Figure 7. The pErk1/2 levels in response to FGF21 in different tissues from wild-type and KLB2/2 mice (A) as compared to PBS control, or in the adipose tissue and liver from the FGFR1 floxed (Flox) and CN mice (B) as compared to FGF19 and PBS were determined by immunoblot analyses. Data are representatives of 4–6 mice for each treatment scheme in each genotype group. The average relative activation level of Erk1/2 for each type of tissue is expressed as percentage to the peak activation in WAT of the Flox mice treated with FGF21, after normalized as ratio of pErk1/2 to total Erk1/2 (A) or ratio of pErk1/2 to b–Actin (B). doi:10.1371/journal.pone.0033870.g008 Figure 9. Tissue-specific expression of FGFRs and KLB. Tissues as mentioned in Figure 8 were isolated from healthy C57/BL6, and total RNA extracted was used for qPCR analyses of the expression of FGFR1–4 and KLB. Normalized expression levels were expressed as folds of difference relative to that of b-Actin detected in each sample, and multiplied by 104 for graphic presentation. Data were presented as the mean of triplicates 6 S.D. Inset: small scale plot on y-axis of expression levels in skeletal muscle. doi:10.1371/journal.pone.0033870.g009 PLoS ONE | www.plosone.org 9 March 2012 | Volume 7 | Issue 3 | e33870