OBJECTIVES: Bile salts have been shown to decrease the absorption of methotrexate in the rat intestine by an unknown mechanism. We aimed to examine this effect. METHODS: We assessed apical-to-basolateral (AP-BL) permeation of methotrexate (5 muM) across Caco-2 cell monolayers pretreated with various concentrations (0, 0.25, 0.5, 1, 3 and 5 mM) of sodium cholate or its semisynthetic analogue, sodium 12-monoketocholate. We also determined the effect of orally administered 12-monoketocholate on the intestinal absorption of methotrexate in rats to evaluate a possible in-vitro-in-vivo correlation. KEY FINDINGS: It was found that sodium cholate and sodium 12-monoketocholate decreased the AP-BL permeation of methotrexate at low concentrations (maximal inhibition at 0.25 and 1 mM, respectively) and increased it at higher concentrations. Determination of [(14)C] mannitol permeation and electrical resistance of monolayers during experiments showed that membrane integrity was not compromised at low concentrations of bile salts but was disrupted at higher concentrations. Subsequently, we examined the effect of the simultaneous oral administration of sodium 12-monoketocholate (4, 20, 40 and 80 mg/kg) on the intestinal absorption of methotrexate in rats after an oral dose (5 mg/kg). The pharmacokinetic study showed that 12-monoketocholate at 4 and 20 mg/kg did not change the methotrexate area under the serum concentration-time curve whereas sodium 12-monoketocholate at 40 and 80 mg/kg significantly reduced it. CONCLUSIONS: Sodium 12-monoketocholate appears to decrease the intestinal absorption of methotrexate in rats by inhibition of transcellular active transport.
OBJECTIVES:Bile salts have been shown to decrease the absorption of methotrexate in the rat intestine by an unknown mechanism. We aimed to examine this effect. METHODS: We assessed apical-to-basolateral (AP-BL) permeation of methotrexate (5 muM) across Caco-2 cell monolayers pretreated with various concentrations (0, 0.25, 0.5, 1, 3 and 5 mM) of sodium cholate or its semisynthetic analogue, sodium 12-monoketocholate. We also determined the effect of orally administered 12-monoketocholate on the intestinal absorption of methotrexate in rats to evaluate a possible in-vitro-in-vivo correlation. KEY FINDINGS: It was found that sodium cholate and sodium 12-monoketocholate decreased the AP-BL permeation of methotrexate at low concentrations (maximal inhibition at 0.25 and 1 mM, respectively) and increased it at higher concentrations. Determination of [(14)C] mannitol permeation and electrical resistance of monolayers during experiments showed that membrane integrity was not compromised at low concentrations of bile salts but was disrupted at higher concentrations. Subsequently, we examined the effect of the simultaneous oral administration of sodium 12-monoketocholate (4, 20, 40 and 80 mg/kg) on the intestinal absorption of methotrexate in rats after an oral dose (5 mg/kg). The pharmacokinetic study showed that 12-monoketocholate at 4 and 20 mg/kg did not change the methotrexate area under the serum concentration-time curve whereas sodium 12-monoketocholate at 40 and 80 mg/kg significantly reduced it. CONCLUSIONS:Sodium 12-monoketocholate appears to decrease the intestinal absorption of methotrexate in rats by inhibition of transcellular active transport.