Abstract
Basal-lateral membranes were separated in a selforienting Percoll (modified colloidal silica) gradient from a heavy microsomal membrane fraction by centrifugation at 48,000g for 0.5 h. The (Na+-K+)-ATPase activity as a marker enzyme for the basallateral plasma membrane was 20-fold enriched by this procedure. The adenylate-cyclase activity measured in the basal-lateral membrane fraction was stimulated 6-fold by parathyrin and only up to 1.5-fold by arginine-vasopressin, calcitonin, or isoproterenol. The yield of basallateral plasma membranes was 5 to 10 percent of the amount initially present in the homogenate. The method is also applicable to the pig kidney.