Inhibition by doxycycline of vWF proteolysis. (A) Doxycycline-inhibited proteolytic cleavage of R834W vWF mutant. Autoradiographs of a 1.5% SDS agarose gels probed with ¹²⁵I-labeled anti-vWF. Lanes 1 through 4 and lanes 5 through 8, R834W vWF mutant incubated with 1 U/mL proteinase without and with 2 mmol/L doxycycline, respectively, for 15 minutes (lanes 1 and 5), 30 minutes (lanes 2 and 6), 60 minutes (lanes 3 and 7), and 90 minutes (lanes 4 and 8). (B) Doxycycline prevented the decrease of R834W vWF Rcof activity by the plasma proteinase. vWF ristocetin cofactor (RCof) was expressed as the percentage of the vWF incubated with TBS. (▪) R834W vWF + proteinase treated with 2 mmol/L doxycycline. (♦) R834W vWF + proteinase.