Mast cells (MC) are frequently increased in neoplasias. Recently, we observed that MC from peritoneal cavity of normal mice (NMC) and one of their mediators (heparin) decreased M3 tumor incidence and tumor cell proliferation in vitro, while MC from peritoneal cavity of tumor-bearing mice (TMC) had no effect. The purpose of this study was to evaluate the differences in morphology and content of sulfated glycosaminoglycans between NMC and TMC. Both were stained with Mayer's haematoxylin-Rubipy [tris (2,2'-bipyridine) ruthenium (II)] sequence, a specific technique to detect sulfated polysaccharides. Image processing and analysis (IPA) confirmed densitometric and microfluorometric studies and revealed several structural characteristics of MC. TMC were partially degranulated with smaller surface and greater perimeter than NMC. Shape factor, which reflects the sphericity grade of the cell (1 = spherical), was three-fold increased in TMC in relation to NMC (6.15 vs 1.76, respectively). Also, TMC had less than a half sulfated polysaccharides compared to NMC. We conclude that subcutaneous tumor grafts mediate degranulation of MC from peritoneal cavity with the consequent release of MC mediators such as heparin. This may be one of the factors for the absence of antitumoral effect of TMC.

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