Cytoskeleton involvement on intestinal absorption processes

It has been recently demonstrated in the laboratory that the cytoskeletal i nhibitor cytochalasin E has an indirect inhibitory effect on the function o f the intestinal Na+-sugar cotransporter (SGLT1). The present work confirms that cytochalasin E inhibits SGLT1 activity through cytoskeleton disruptio n, showing that in anaerobic conditions (N-2 bubbling), which implies low c ytosolic ATP levels, the inhibition is not observed. As it occurs in sugar transport, the Na+-dependent intestinal transport of phenylalanine decrease s if cytochalasin E is present in the incubation medium. However, the activ ity of the brush border enzymes sucrase, amino peptidase N and gamma-glutam yl transferase is not affected by the inhibitor. These enzymes only have on e transmembrane domain and the active center is projected to the intestinal lumen. Therefore, cytoskeleton changes that could modify the transmembrane enzyme segment do not alter the activity of these enzymes. Examination of the intestine morphology after 30 min incubation with cytochalasin E shows only light modifications which do not seem to explain the inhibitory effect s of the toxin on Na+-sugar or Na+-phenylalanine cotransporters function. O n the whole, these results indicate that the inhibition of cytochalasin E o n galactose and phenylalanine intestinal transport is secondary to its acti on on cytoskeleton through protein structure modifications.