Description:
<jats:p>Binding and transport characteristics for uptake of taurocholic acid by isolated rat liver cells were studied.</jats:p><jats:p>
<jats:list list-type="explicit-label">
<jats:list-item><jats:p>An adsorption of taurocholate to the cell surface is terminated in less than 15 s. A <jats:italic>K</jats:italic><jats:sub>s</jats:sub> of 0.55 mM and a total binding capacity of 3.8 nmol/mg cell protein is determined.</jats:p></jats:list-item>
<jats:list-item><jats:p>The rate of uptake of taurocholate follows Michaelis‐Menten kinetics with <jats:italic>K</jats:italic><jats:sub>m</jats:sub>= 19 μM and <jats:italic>V</jats:italic>= 1.7 nmol/mg protein min.</jats:p></jats:list-item>
<jats:list-item><jats:p>There is a broad pH optimum for uptake between pH 6.5–8.0.</jats:p></jats:list-item>
<jats:list-item><jats:p>The activation energy amounts to 29 kcal/mol. At high taurocholate concentration an unusual upward bend is observed in the Arrhenius plot.</jats:p></jats:list-item>
<jats:list-item><jats:p>Taurocholate uptake is competitively inhibited by taurochenodeoxycholate (<jats:italic>K</jats:italic><jats:sub>i</jats:sub>= 9 μM). It is noncompetitively inhibited by bromosulfophthalein (<jats:italic>K</jats:italic><jats:sub>i</jats:sub>= 3 μM).</jats:p></jats:list-item>
<jats:list-item><jats:p>At physiological taurocholate concentrations a 200‐fold intracellular accumulation of taurocholate is observed.</jats:p></jats:list-item>
<jats:list-item><jats:p>Uptake is inhibited by about 75% by either antimycin A, carbonylcyanide <jats:italic>m</jats:italic>‐chlorophenyl‐hydrazone, ouabain.</jats:p></jats:list-item>
<jats:list-item><jats:p>Replacement of extracellular Na<jats:sup>+</jats:sup> by either K<jats:sup>+</jats:sup> or sucrose results in a 75% decrease of uptake.</jats:p></jats:list-item>
<jats:list-item><jats:p>It is concluded that taurocholate uptake is a carrier‐mediated process, and suggested that the energy for intracellular accumulation is made available by cotransport of Na<jats:sup>+</jats:sup>.</jats:p></jats:list-item>
</jats:list>
</jats:p>