The Partition of Manganese Among Organs and Intracellular Organelles of the Rat

The essential metabolic r61e of manganese in the animal organism has long been a matter of record. It was an early finding that intravenously injected manganous salts are removed quickly from the blood stream (l), leaving the body somewhat less rapidly by way of t,he biliary tract (2). In the course of studies on the kinetics of manganese, our observations led us to surmise the existence in the body of a mechanism whereby the manganese is temporarily diverted in transit, entrapped, and then gradually released. Such a mechanism, with the resulting rapid movement of the element into the entrapping system, would provide an explanation for the lack of agreement noted in previous studies of this metal’s distribution in organs (3-7). The isotope used in this study, Mn 66, has the advantage of being readily available to us in sufficiently high specific activity so that dosages need not exceed levels of normal tolerance. The short half life of this materia.! confined our attention to the early portion of the distribution process, before reabsorption and redistribution of the isotope became a factor to confuse interpretation of the results. From distribution studies in organs, a correlation became apparent between the richness in mitochondria of a given organ and its ability to concentrate manganese. We, therefore, extended our studies to include the mitochondrial uptake of this element in vivo, to determine whether these organelles were a preferential site of manganese accumulation and presumably of its metabolic activity.