HISTAMINE-LIBERATION IN MOUSE AND RAT 



At this stage there is an absolute decrease in the number of mast cells in 

 both ear and subcutis, such cells as remain being recognizable only by the 

 presence of a few clumped granules or of small pale granules situated at the 

 periphery of greatly swollen 'ghost' cells. At day five there is no further 

 visible damage to the mast cells, and signs of itching, cyanosis and oedema 

 are no longer provoked. 



In as short a time as six days after the last injection (day eleven of the 

 experiment) there is substantial restoration of the mast-cell pattern in the skin 



IOO 



80- 



60 



40- 



20- 



1 j 11 inn 11 

 O 5 



- 1 — 

 IO 



— 1 — 

 20 



— 1— 

 25 



— 1 — 

 30 



—1 



35 



DAYS 



Fig. 41 



Short-term experiment. Effect of compound 48/80, given over five days, on the 

 histamine content of subcutaneous connective tissue (dotted lines) and ears (solid 

 lines) of mouse and rat: histamine values expressed as per cent of normal. 

 Compound 48/80 is about twice as effective in the rat as in the mouse. Both 

 species recover rapidly. 



of the ear and especially in the subcutis, and it is noteworthy that these are 

 almost all large, adult cells though poor in granules. This histological recovery 

 is also matched by a rise in the tissue histamine, the ear showing a restoration 

 to about 24 per cent of its normal value, whereas the subcutis is restored to about 

 39 per cent of normal. By day eighteen the two tissues are refilling with mast 

 cells of normal adult size though again the ears tend to show a slower rate of 

 recovery than the subcutaneous connective tissue. At this stage the histamine 

 content of the ears is 50 per cent of normal, whereas the histamine in the sub- 

 cutis is almost fully restored. By day thirty-two recovery is complete in both 

 regions studied (Fig. 41). 



Ill 



