The Ultrastructure of Isolated and in Situ Human Cardiac Age Pigment

The occurrence of fluorescent, pigmented inclusion bodies in muscle, nerve, and other non-dividing cell lines has been known since the turn of the century. These pigments, variously known as age pigments, lipofuscin, or abnutzungspig-mente (wear and tear pigments), have been subjected to numerous histochemical and histo-logical studies. Little has been firmly established, however, regarding the relationship of these structures to the normal aging process even though the pigment in large amounts is a normal concomitant of aging in a number of different cell lines. A report from this laboratory (1) established the first quantitative relationship between chronological age and the amounts of age pigments in human cardiac muscle. It was shown that the concentration of this substance increased at the rate of about 0.3 per cent of a total heart volume per decade or 0.6 per cent of the intra-cellular volume per decade. Thus in a centenarian the expected average pigment concentration would be approximately 6 per cent of the total intra-cellular volume. The concentration of pigment in this study, in contrast to that of Bachmann's study (2) on human liver lipofuscin, was not shown to be significantly altered by the clinical history of the individuals autopsied. During the past four years we have developed methods for obtaining purified preparations of age pigment utilizing homogenization, sonication, KCI extraction, and centrifugation techniques, and have described a number of the physical and chemical properties of this purified material (3, 4). Similar studies have been conducted by Heiden-reich and Siebert (5). Chemical and physical analyses of this purified pigment (3) indicate that it consists of autooxidized lipids in association with a protein moiety. The relationship of lipofuscin granules to pre-existing or known cell organelles has been the subject of some discussion. It has been suggested (6), on the one hand, that they arise from the deterioration of mitochondria, primarily because bodies which have been identified as lipofuscin granules occasionally can be conjugant with partially disorganized mitochondria and may occasionally have double membranes surrounding them. On the other hand, the work of Essner and Novikoff (7) and of Gedigk and Bontke (8) has strongly suggested a relationship or identity between lipofuscin and lysosomes, since the pig-mented areas in liver, cardiac muscle, brain, and elsewhere were shown by histochemical tests to be the loci of acid phosphatase and catheptic activity. The lipofuscin we have isolated from human cardiac muscle was, contrary to expectation, found not …