Lipocortin IV is a basolateral cytoskeleton constituent of rabbit enterocytes

A monoclonal antibody, BL7B1, which specifically recognized rabbit lipocortin IV, was produced. The BL7B1 epitope is localized between the methionine residues that occupy positions 148 and 259 in human lipocortin IV. Immunofluorescence and subcellular fractionation studies showed that in the rabbit enterocytes, lipocortin IV is specifically associated with the basolateral membranes. When these membranes are solubilized by Triton X-100 in the presence of 1 mM of Ca2+ the lipocortin IV, like the cytoskeleton, remained insoluble suggesting that it might be associated with this structure in vivo. No lipocortin IV was detected in the brush border using immunofluorescence techniques and less than 10% of the amount present in the purified basolateral membranes was detected in the brush border membrane fraction.