A simple and fast method for the isolation of basolateral plasma membranes from rat small-intestinal epithelial cells.

A method was developed for the analytical and preparative isolation of basolateral plasma membranes from rat small intestine. They were separated on a self-orientating Percoll (modified colloidal silica) gradient starting with a heavy microsomal-membrane fraction and involving centrifugation at 48,000 g for 1 h. (Na+ + K+)-stimulated ATPase activity, used as a marker enzyme for the basolateral plasma membrane, is enriched 20-fold compared with that found in the homogenate of isolated intestinal epithelial cells.

[Uptake of L-(+)lactate by cell membrane (luminal and contraluminal) isolated from rat small intestine microvilli]. / Uptake di L-(+)lattato in membrane plasmatiche (luminali e contraluminali) isolate de enterociti di intestino tenue di ratto.

L-lactate uptake was measured in vesicles formed by intestinal brush border and baso-lateral membranes, using a rapid filtration technique. In the presence of a Na+ gradient directed into the vesicle, L-lactate can be transiently accumulated in brush border vesicles, but not in baso-lateral ones. The transient L-lactate accumulation does not occur in the presence of a KCl gradient. alpha-cyanocinammic acid strongly inhibits L-lactate uptake in brush border vesicles, but not in baso-lateral ones. These results support the existence of a carrier mediated, Na+ dependent, transport of L-lactate across the brush border membrane.