Comparative study on brush border membranes prepared from rat and monkey small intestine by Ca2+ and Mg2+ precipitation.

Brush border membranes, prepared by Ca2+ or Mg2+ precipitation, from monkey or rat small intestine were compared for marker enzyme enrichment and lipid composition. Membranes prepared from rat intestine by Mg2+ precipitation were less pure in terms of their marker enzyme enrichment than Ca2+ precipitated membranes. Moreover, Mg2+ precipitated membranes were contaminated by basolateral membranes as evidenced by the enrichment of Na(+)-K+ ATPase. The content and composition of phospholipids were different in Mg2+ and Ca2+ precipitated membranes. The membranes prepared by the two methods from monkeys were identical in their marker enzyme enrichment and lipid composition and unlike those obtained from the rat, there was no basolateral membrane contamination.