A tracer technique which was developed for studies on amino acid uptake in brain has been used to investigate the uptake of 14C labeled substances by liver. AAn 0.2 ml bolus of test solution containing 1-2 μCi of 14C amino acid and 3-6 μCi of 3HOH (as an internal reference standard) was administered by rapid portal injection in anesthetized rats. Circulation was terminated after a single passage of the bolus through the hepatic microvasculature and the tissue was immediately subjected to liquid scintillation counting. Liver uptake indices (LUI) were calculated from the ratio of 14C to 3H in liver tissue relative to the same ratio in the injection mixture. LUI's of the substances tested were arranged in a spectrum between inulin (22.5%), sucrose (24.3%), D mannitol (80.2%) and D glucose (138.0%). For the amino acids, LUI's were highest for the acidics (L Asp, 107.3%; L Glu, 84.05%) and lowest for the basics (L Arg, 37.4%; L lys, 31.4%). Stereospecificity (L Ala, 41.2%; D Ala, 22.7%), saturation kinetics (Km for L Glu, 4.8 mM), and competition demonstrated the applicability of this method for characterizing amino acid transport systems in liver.
|Original language||English (US)|
|Number of pages||1|
|Issue number||3 (I)|
|State||Published - Jan 1 1973|
All Science Journal Classification (ASJC) codes