130 



Exposure of the two cell lines for 15 minutes to ADGG- 

 Con A, ADGG and Con A resulted in the inhibition shown in 

 Table 10. Con A at 40yg/ml caused approximately 10% inhi- 

 bition of growth in both A-9 and LAN~2 cells. Free ADGG 

 did not affect LAN 2 cells and at 2.5 x 10 M had a marginal 

 effect on the growth of A-9 (12% inhibition) . ADGG-Con A 

 again demonstrated greatly enhanced cytotoxicity with 40% 

 inhibition of A-9 cells occurring at 1 x 10 M ADGG-Con A. 

 At the same concentration of ADGG-Con A, LAN- 2 cells dis- 

 played 13% inhibition, almost an identical amount to that 

 obtained with the same concentration of Con A alone (11% at 

 40ug/ml) . These results strongly imply that the toxicity 

 of ADGG-Con A is due to the specific inhibition of RNA 

 polymerase II by the a-amanitin protein of the conjugate. 



