x1 = C_para_Apical
x2 = C_para_Caco_2
x3 = C_para__Basolateral___HepG2_
x4 = C_sulf_Apical
x5 = C_sulf_Caco_2
x6 = C_sulf__Basolateral___HepG2_
x7 = C_glu_Apical
x8 = C_glu_Caco_2
x9 = C_glu__Basolateral___HepG2_