Association of ferritin with liver cell membrane fractions.

Following intraperitoneal injection of rats with a large dose of ferric ammonium citrate containing ⁵⁹Fe, some 35 to 50% of the dose was deposited in the liver within the first 1 to 4 h. Almost all of the deposited iron could be precipitated with a ferritin antiserum from a homogenate of liver heated to 75 °C, but only half of this was precipitable when the unheated homogenate was treated with antiserum. The remainder of the ferritin iron was made available to the antiserum by treatment with deoxycholate, and was therefore presumed to be associated with membranous components of the cell.Subcellular fractionation of the liver following administration of ⁵⁹Fe-labeled ferric ammonium citrate showed that most of the radioactivity deposited within the first 4 h was equally divided between the cell sap and a light microsome (membrane-rich) fraction. Ferritin in this latter fraction was made available to antibody following deoxycholate treatment. The liver microsome fraction of the young rat contains little unavailable ferritin, but with aging there is an accumulation of ferritin in the microsomal fraction which is unavailable to antibody until the membrane is removed.It is suggested that at least part of the injected iron salt is taken up by pinocytotic vesicles and transferred to ferritin within this fraction, possibly followed by release of some of this ferritin into the cell sap.