Figure 2

The carnitine transporter OCTN2 and carnitine uptake in MDBK cells is regulated by PPARβ/δ. A, Effect of treatment with 1 μM of GW0742 for 24 h on mRNA levels of CPT1A and PPARD. B-E, Effect of treatment with 1 μM of GW0742 for 24 h in the absence (B, C) and presence (D, E) of PPARβ/δ selective antagonist GSK3787 (10 μM) on relative mRNA (B, D) and protein levels (C and E) of OCTN2. A, B and D, Bars represent means ± SD of three independent experiments and are expressed as fold of DMSO-treated control cells. C and E, Bars represent data from densitometric analysis and are means ± SD of three independent experiments. Immunoblots specific to OCTN2 and β-Actin as internal control are shown for one independent experiment; immunoblots for the other experiments revealed similar results. Data represent means ± SD of three independent experiments and are expressed as fold of DMSO-treated control cells. *Different from DMSO-treated control, P < 0.05. F and G, Effect of treatment with 1 μM of GW0742 on uptake of L-[³H]-carnitine (10 nM, specific radioactivity 80 Ci/mmol). F, Uptake of L-[³H]-carnitine by MDBK cells treated for 24 h with either GW0742 or DMSO (control) at different Na⁺ concentrations (0, 25 and 125 mM NaCl) was studied over 30 min. G, Uptake of L-[³H]-carnitine by MDBK cells treated for 24 h with either GW0742, GW0742 together with GSK3787 (10 mM) or DMSO (control) at 125 mM NaCl was studied over 30 min. Data represent means ± SD of three independent experiments each performed in triplicate. ^a,b,cData with different superscript letters differ, P < 0.05. *Different from DMSO-treated control, P < 0.05.