Light- and electron-microscope studies of the effects of 4-aminopteroylglutamic acid (aminopterin) on the mucous membrane of the small intestine of the rat

Aminopterin, a cytotoxic agent, causes mitotic arrest by interfering with the catabolism of ribonucleoprotein. The effects on the small intestine are demonstrated. The resulting atrophy, with changes in the microvilli, is associated with severely impaired fat absorption.