THE MAST CELLS 



chronic inflammation elsewhere. Yet when I came to implant some of the 

 carcinogens directly into the dermis the mast-cell reaction was distinctly less 

 than when the carcinogen reached the dermis by way of the overlying epidermis. 

 The inference is that something in the epidermis is responsible for the dermal 

 changes, including the mast-cell reaction. Cortisone can largely suppress the 

 dermal reaction to a surface carcinogen, though intra-epithelial tumours may 

 still arise (Gillman et al, 1955). However, should a papilloma develop despite 

 the administration of cortisone, it is accompanied by the usual mast-cell 

 reaction in the dermis (Engelbreth-Holm and Zachariae, 1953). 



Recently we have uncovered fresh facts which go some way towards 

 explaining both the mast-cell reaction and the golden-brown fluorescence. 



At the Histamine Symposium (April 1954) I stated in discussion that I 

 thought it unlikely that mast cells, in general, contain substances other than 

 histamine which act on plain muscle; thus, the published data concerning the 

 topographical distribution of 5-hydroxytryptamine (5-HT) did not then seem 

 to fit the pattern shared in common by the mast cells and histamine. Shortly 

 afterwards we ourselves examined several of the types of specimen which had 

 proved so useful in clinching the mast cell-histamine hypothesis, e.g. ox liver 

 capsule, mast-cell tumours from dogs and cattle, urticaria pigmentosa from man. 

 All were negative for 5-HT or contained only the merest traces. 



However, as Benditt (1955) and others have shown, 5-HT is present in the 

 mast cells of two species, the mouse and rat. Moreover, it seems that 5-HT is 

 also present in the epidermis of these two species (West and Parratt, 1957). 



In order to demonstrate 5-HT in the mast cells, Miss Cass, Dr. Marshall 

 and I examined selected tissues from both rat and mouse. Our point was to 

 use tissues remote from either gut or epidermis, lest the mast cells be con- 

 taminated by 5-HT from some other source (Cass et al, 1958). 



For the rat, we chose the metaphyses of the long bones which normally 

 have no mast cells, but which acquire them in great numbers in parallel with 

 the development of a triple syndrome of decalcification-rickets-osteitis fibrosa, 

 induced by dietetic means (Urist and McLean, 1957; and see Figs. 64, 65). 

 Briefly, our results were in agreement with the claims of Benditt: 5-HT and 

 mast cells appeared together in the bones, as of course did histamine and the 

 mast cells. 



For the mouse, we first used dermal scrapings from skin treated with a 

 carcinogenic hydrocarbon, despite the legitimate objection that such a tissue 

 is close to epidermis which may itself contain 5-HT. Any doubts regarding 

 the significance of the result were settled when we obtained from Dr. Jacob 

 Furth of Boston, a sample of a transplantable mouse mast-cell tumour, recently 

 isolated by him from a group of mice which had been subjected to ionizing 

 radiation. So high were the values for histamine, heparin and 5-HT in the 



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