Urinary Elimination of Bile Acid Glucuronides under Severe Cholestatic Situations: Contribution of Hepatic and Renal Glucuronidation Reactions

Figure 4

Kinetic analyses of LCA-3G (a), LCA-24G (b), DCA-3G (c), and DCA-24G (d) formation by microsomes from human liver and kidney. Human liver (black squares, pool of 50 donors) and kidney (white diamonds; pool of 8 donors) microsomes (10 μg) were incubated in the presence of increasing concentrations (1 to 350 μM) of lithocholic acid (LCA, (a) and (b)) or deoxycholic acid (DCA, (c) and (d)) for 2 hours at 37°C. The formation of LCA-3G (a), LCA-24G (b), DCA-3G (c), and DCA-24G (d) was analyzed by LC-MS/MS. For each panel, graphs represent the rate of product formation (-axis) versus substrate concentration (-axis) of two experiments performed in triplicate. The listed kinetic parameters were determined as indicated in “Materials and Methods.” : constant of inhibition expressed as μM; : calculated Michaelis constant expressed as μM; : calculated maximal velocity expressed as nmol/h/mg proteins; : Hill coefficient.

(a)

(b)

(c)

(d)