Materials and Reagents

1. Mouse liver
   
2. ¹⁴C-labeled amino acids (PerkinElmer) (select the amino acid of your interest)
   
3. 3 N methanolic HCl (Sigma-Aldrich, catalog number: 33051 )
   
4. Anhydrous methanol (Sigma-Aldrich, catalog number: 322415 )
   
5. Sucrose
   
6. HEPES
   
7. MOPS
   
8. Na₂EDTA
   
9. KCl
   
10. MgCl₂
    
11. ATP-Mg
    
12. Phosphate buffered saline (PBS)
    
13. Scintillation cocktail (Research Products International, catalog number: 111175 )
    
14. Protein assay kit (Bio-Rad Laboratories, catalog number: 500-0112 )
    
15. Homogenization buffer (HB) (see Recipes)
    
16. High sucrose buffer (see Recipes)
    
17. Uptake buffer (see Recipes)
    
18. Efflux buffer (see Recipes)
    

Equipment

1. Nitrogen gas tank (with regulator and connecting tube)
   
2. 25-ml glass conical flask
   
3. 1.5 ml and 15 ml tubes
   
4. 30 G needles
   
5. Dounce homogenizer
   
6. High speed centrifuge (up to 25,000 x g) with temperature control
   
7. Glassfiber filters (Grade GF/F) (Whatman, catalog number: 1825-025 )
   
8. Vacuum filtration manifold (EMD Millipore, model: 1225 )
   
9. Liquid scintillation counter (Beckman Coulter, model: LS6500 )
   
10. Personal protective equipment for working with radioactive materials
    

Procedure