Figure 3.

(A) NTPPH and alkaline phosphatase activity. Apoptotic bodies (AB), matrix vesicles (MV), and mixtures of apoptotic bodies and matrix vesicles (AB/MV) were prepared as described in the legend to Fig. 2. Identical amounts of protein were assayed for NTPPH and alkaline phosphatase (ALK PHOS) activities. (B) Chondrocyte apoptotic bodies contain the PP_i-generating enzyme PC-1. Apoptotic bodies sedimented by ultracentrifugation from SNP-treated chondrocytes were lysed in Triton X-100 and analyzed by SDS/PAGE under reducing conditions and Western blotting, using the polyclonal antibody 1769, as previously described (25).The figure shows a Western blot analysis of 10 μg of protein from the apoptotic bodies. The dark arrow indicates the detection of full-length PC-1 monomer (130 kDa); the smaller arrow indicates the presence of a larger PC-1 species of 260 kDa, attributable to incomplete reduction of PC-1 homodimers as previously observed (23).