Competitive inhibition between folic acid and methotrexate for transport carrier in the rat small intestine.
Folic acid absorption from the lumen of the rat small intestine in situ obeyed Michaelis--Menten kinetics. The values of Vmax and Km for absorption were 4.63 x 10(-7) M/min and 1.21 x 10(-6) M, respectively. Folic acid and methotrexate were mutual competitive inhibitors of absorption. Their Ki values were 1.28 x 10(-6) and 1.9 x 10(-5) M, respectively.
D000818:Animals; D001667:Binding, Competitive; D005492:Folic Acid / Q000378:metabolism*; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008727:Methotrexate / Q000378:metabolism*; D051381:Rats
D005492:Folic Acid; D008727:Methotrexate