Fig. 2.

CTSB activity in U937 cells was increased by growth in 231-CM. U937 cells were grown in the absence (control) or presence of different concentrations of 231-CM for 3, 5 and 7 da (treated). CTSB activity in cell lysates (A) and in media (B) was measured against Z-Arg-Arg-NHMec and is expressed as pmol/min/μg DNA. Activity in the media was measured after pepsin activation of proCTSB as described in Materials and Methods. Data represent mean ± S.D. of at least three independent experiments; *, p = 0.05 (as compared to the control at each time interval).