THE PIGMENT OF MELANOSIS COLI - A LECTIN HISTOCHEMICAL-STUDY

Citation
Sh. Benavides et al., THE PIGMENT OF MELANOSIS COLI - A LECTIN HISTOCHEMICAL-STUDY, Gastrointestinal endoscopy, 46(2), 1997, pp. 131-138
Citations number
51
Categorie Soggetti
Gastroenterology & Hepatology
Journal title
ISSN journal
00165107
Volume
46
Issue
2
Year of publication
1997
Pages
131 - 138
Database
ISI
SICI code
0016-5107(1997)46:2<131:TPOMC->2.0.ZU;2-R
Abstract
Background: The compositional nature of the pigment of melanosis coli is essentially unknown. Previous histochemical studies suggested that this pigment has certain similarities with lipofuscin (i.e., age-depen dent pigment) and ceroids (i.e., pathologically derived pigments) and that it may contain, therefore, polymerized glycolipids and glycoprote ins. However, the saccharide composition of this pigment was never exp lored by lectin histochemical procedures, which was the main object of this study. Methods: Colonoscopic biopsy specimens from eight patient s with melanosis coli and from three normal control subjects were stud ied by fluorescent microscopy and by standard and lectin histochemistr y. The number of apoptoses in the lining colonic epithelium was also e valuated histologically. Results: Apoptotic bodies were significantly more numerous in patients with melanosis coli than in control subjects . The pigment that accumulates in macrophages of the lamina propia sho wed autofluorescence, sudanophilia, acid-fastness, and positiveness to PAS and Schmorl's reactions, all of which are common to lipofuscin an d ceroids, plus an intense argentaffin reaction abolished by bleaching , indicative of a melanic substance. Lectin histochemistry showed, in decreasing order of frequency, the presence of alpha-D-mannose, sialic acid, beta-D-galactose (lactose), gal-beta-(1-3)acetyl-galactosamine, alpha-D-galactose, and alpha-L-fucose, but no terminal alpha-D-acetyl -galactosaminyl residues. Conclusions: The significant increase of apo ptotic bodies in the lining colonic epithelium indicated that this typ e of cell death is not due to the natural programmed cell renewal, but to the action of laxatives. Because the autofluorescent pigment of me lanosis coli contains melanin (as well as glycoconjugates) and is not dependent on age but on the use of anthranoid laxatives, it should be categorized as a ''melanized ceroid.'' The lectin affinities of this p igment indicated that it contains a substantial number of saccharide r esidues almost similar to those found in the ceroid pigment of human a ortic atheromas. These findings and considerations on the metabolism a nd pharmacokinetics of anthranoids suggested that the apoptotic epithe lial cells, rather than the laxatives, may be the source of the pigmen t saccharides, whereas the precursors of the melanic substance may be derived from the anthranoids.