Fig. 6. Purified MMPs cleave PRL. Reducing (A) and non-reducing (B) western blot analysis of proteolytic products generated from PRL by incubation of 200 ng of human PRL with 2 µg of protein of rat chondrocyte lysate (L), rat chondrocyte-conditioned medium (CM), or with the indicated amount (ng of protein) of purified MMP-8, MMP-13, MMP-3, MMP-1, MMP-2 or MMP-9. The non-incubated human PRL standard (PRL std) is shown. Arrows indicate the various PRL proteolytic products and their relative molecular mass is indicated on the left of western blots. (C) The densitometric values of the 16-kDa-PRL and 17-kDa-PRL fragments generated by incubation with various concentrations of the purified MMPs were expressed as percentage of that of the 23-kDa-PRL band in the non-incubated PRL standard.