127 



-7 



the ID of 2.1 x 10 M for H-7 cells. The inhibition of 

 H-7Wcr cells obtained with free ADGG and a-amanitin was 

 somewhat different than the minimal inhibition seen for 

 H-7 cells and ADGG. Both ADGG and a-amanitin had a cyto- 

 toxic effect on the H-7Wcr cells after a 15 minute exposure. 

 The inhibition was essentially the same for both compounds 

 over the entire range of concentrations in contrast to the 

 continuous exposure data. At the maximum dose tested, 2 x 

 10 M, ADGG gave 40% inhibition, a-amanitin 50% inhibition 

 and conjugated ADGG- Con A gave 82% inhibition. 



The ADGG-Con A clearly has more cytotoxic potential 

 than either of the unconjugated inhibitors for both CHO cell 

 lines. In order to verify that the conjugate toxicity is 

 due to Con A mediated targeting of the a-amanitin portion of 

 the conjugate and not some unique property of the conjugate 

 itself, an a-amanitin resistant cell line, LAN- 2 , and its 

 normal parent line, A-9, were tested for sensitivity to 

 ADGG-Con A, Con A, ADGG and a-amanitin. 



The effects on A-9 and LAN-2 cells of continuous 

 exposure to a-amanitin and ADGG are presented in Figure 28. 

 The LAN-2 cells were entirely refractory to inhibition by 



either ADGG or free a-amanitin up to the maximum dose 



-5 . . 



tested (1.6 x 10 M) . The parent cells, A-9, were inhibi- 

 ted by both ADGG and a-amanitin and as was found with CHO 



cells, a-amanitin (ID rri = 5.4 x 10 M) was more toxic than 



50 



ADGG (extrapolated ID = 2.1 x 10~ M) . 



