FUNCTION OF HEPARIN 



< 1941, 1957), following the lead of Staemmler (1921), believes that the mast cell 

 produces the metachromatic ground substance ('free chromotrope substance') 

 of granulation tissue. Asboe-Hansen (1951, 1954) states even more emphatic- 

 ally that the mast cell, under hormonal control, secretes the hyaluronic acid of 

 the ground substance, perhaps by way of a heparin-like precursor. But the facts 

 ( 1 ) that in normal development in the embryo and in chronic inflammation 

 in the adult, the metachromatic ground substance is laid down before the mast 

 cells appear, and (2) that fibroblasts and synovial cells in vitro are capable of 

 forming hyaluronic acid in the medium without the participation of mast cells, 

 both tend to shift the initiation of the production of ground substance to the 

 connective tissue cells themselves (Campani, 1951; Grossfield et al, 1955; 

 Taylor and Saunders, 1956; Castor, 1957). According to Meyer (1950, p. 32): 

 'fibroblasts secrete large amounts of acid mucopolysaccharides together with 

 a globular native protein, the precollagen. . . . The regularly spaced acidic 

 groups of the polysaccharide chain would form a template, so to speak, on 

 which the fibrous proteins are built. The mucopolysaccharides which first 

 form a sheath on the fibrils would then be removed by enzymatic digestion.' 

 It is at this stage that the mast cells appear: the mastocytosis is a secondary 

 event (Riley, 1954). 



Endothelial cells, mesothelial cells, synovial cells and fibroblasts have much 

 in common (Grossfeld et al, 1955). Synovial joints develop as clefts in the 

 embryonic mesenchyme; adventitious bursae readily form in the connective 

 tissue of the adult. Even the vascular endothelial cell is now believed to 

 furnish its own coat of sulphated mucopolysaccharide (Curran, 1957). A 

 surface secretion of a cell in one situation is an intercellular secretion in another. 

 And in every case it is possible to envisage a final concentration and storage of 

 altered mucopolysaccharide in the granules of tissue mast cells. Under suitable 

 circumstances the granular mucopolysaccharide can again be released and find 

 its way back into the fibroblast (Fig. 54). At the same time, it is clear that the 

 metachromatic substance of the mast cell is but one source of fuel for the 

 connective tissue cell and that the mast cell, in turn, can flourish in the absence 

 of fibroplasia, as in the mast-cell tumours. Nevertheless, there are grounds 

 for the belief that a local mast-cell cycle may operate in the tissues and that this, 

 in turn, is geared to the major cycle of lymph and blood. In any event, the 

 emergent route for heparin from the mast cell must surely be by way of the 

 lymphatics. 



More facts are needed for a final evaluation of the role of the mast cell in 

 the connective tissues. For the moment we must leave it that a local 'mast- 

 cell cycle' may play its part in the deposition, absorption and redeposition of 

 fibrils in connective tissue and that there is growing evidence that this is so. 



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