Effect of Aminopterin on the Absorption of Fat into the Lymph of Unanesthetized Rats

Summary The effect of aminopterin on fat absorption into the lymph of unanesthetized rats has been studied at various times after the administration of the drug. A consistent effect on fat absorption has been shown, and this has been related to the age of the mucosal cells. After inhibition of mitosis with aminopterin, fat absorption remains normal for at least 32 hr, and then there follows a period of severe malabsorption which lasts for 2 days. This malabsorption has been shown to be mucosal in origin. Mitosis in the crypts recommences on the fourth day after aminopterin, but fat absorption does not begin to recover until about 24 hr later. The results indicate that a preliminary correlation of mucosal cell age to fat absorption is possible. Newly arisen cells appear to be unable to absorb fat until they are about 24 hr old, and then they retain this ability until they are due to be shed from the tips of the villi.