W. J. DODDS AND L. W. HOYER 
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100 r 
FACTOR VIII DEF. HUMAN PLASMA 
100 
J L 
4 0 
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TIME (Hrs.) 
2 3 
(b) 
Figure 5. — a. Splenic factor VIII activities after addition of 5 ml fresh-frozen factor VIII deficient human plasma as 
indicated by the arrow. Activity of 4 perfusions in each group. CRM( + ) hemophilia A plasma (A A); 
CRM( — ) hemophilia A plasma (A A); von Willebrand's disease plasma (X X). b. Splenic factor IX 
activities of the same perfusion experiments shown in 5a. CRM( + ) hemophilia A plasma (• •) ; CRM(— ) 
hemophilia A plasma (O O) ; von Willebrand's disease plasma (X X). 
are sensitive to puromycin, cycloheximide, and 
actinomycin D.^-^ The results clearly indicate 
that perfusion with plasma is not necessary in 
this experimental model. Small amounts of 
plasma were incorporated into the system, how- 
ever, in order to demonstrate that production of 
activity could be regulated by negative feed- 
back. 
Data shown in Figures 2-6 and the results 
obtained in previous experiments with deficient 
canine plasmas^ support the concept that factor 
VIII and IX production in perfused organs is 
inversely proportional to the level of these coag- 
ulation factors in the perfusate. For example, 
both normal rabbit and human plasma were 
capable of elevating perfusate coagulation activi- 
ties to a level which inhibited further produc- 
tion (Figures 2 and 4). In the case of normal 
human plasma, however, it required addition of 
factor VIII concentrates to achieve this effect 
(Figure 4). These results were anticipated be- 
cause human plasma is 2.5 times less active 
than rabbit plasma with respect to factor VIII 
activity. Similar results in support of the con- 
cept of negative feedback were obtained pre- 
viously with normal and factor VII deficient 
canine plasmas which both contained normal 
levels of factors VIII and IX. ^ A reciprocal re- 
sponse between factor VIII and IX production 
was observed when plasma from warfarin- 
treated rabbits (factor IX deficient) and from 
patients with hemophilia A, hemophilia B, and 
von Willebrand's disease were perfused (Fig- 
ures 3, 5, 6) . Factor IX activity increased in the 
absence of significant change in factor VIII ac- 
tivity when factor IX deficient plasmas were 
perfused, whereas the reverse occurred when 
factor VIII deficient plasmas were used. Factor 
VIII perfusate data obtained with human fac- 
tor IX deficient plasma (Figure 6a) were com- 
plicated by the relatively low factor VIII 
activity in these plasma samples. It was possible, 
however, to reverse this effect on factor VIII 
production by prior addition of factor VIII con- 
centrates to the hemophilia B samples (Figure 
6a) . Experiments reported previously following 
