37 



concentration of luCi/ml 47 hours after addition of inhi- 

 bitors to cultures. The assay was performed in scintilla- 

 tion vials as described for inhibition of cell number by 

 ADH-BSA conjugates. After 1 hour at 37°C, incorporation by 

 AV3 and CHO M-7 cells was stopped by addition of 10ml of 

 ice cold Gey's A. Cultures were washed three times with 

 5.0ml of 1. 5% perchloric acid , once with 95% ethanol and 

 drained. The vials were heated for 40 minutes at 80°C 

 after addition of l.Oml/vial of 5% perchloric acid. This 

 treatment served to hydrolyze the nucleic acids for scin- 

 tillation counting which was done following addition of 

 lOml/vial of a Triton X-100 based scintillation cocktail 



with a Beckman L5-133 counter. 



3 

 Measurement of H-TdR uptake by EL4 cells was accom- 

 plished with a 1 hour exposure to the labeled nucleoside. 

 Collection of the entire culture on GF/C glass fiber filters 

 (prewashed with 1.5% perchloric acid) was performed after 

 stopping incorporation with 1.0ml 3% perchloric acid. The 

 collected precipitates were washed once with 1.5% perchloric 

 acid, three times with ether :ethanol (1:3) , twice with ether, 

 dried at 100°C and counted in a toluene based scintillation 

 cocktail . 



Measurement of Pinocytosis 



125 

 Synthesis of I-RSA . Measurement of the pinocytic 



125 

 activity of AV3, CHO M-7 and EL4 cells by uptake of x ^ J l- 



BSA was performed by modification of the method of Steinman, 



125 

 et al. (1974). I-BSA was prepared by lodination with 



