Vasopressin-induced, cAMP-dependent vWF secretion from HMVEC-L cells. (a) Confluent HMVEC-L grown in 12-well plates were incubated in KRBH for 30 minutes in the presence of DDAVP (1 μM), AVP (1 μM), forskolin (Forsk; 10 μM), or KRBH alone (Contr). The experiments were performed in the absence or the presence of 100 μM IBMX, and vWF released in the incubation medium was assayed by ELISA. Results are shown as relative values, release from control cells being defined as 100%. The data are the mean ± SEM of 10 (DDAVP and forskolin) or four (AVP) experiments. (AP < 0.05 by Student’s paired t test). (b) Confluent HMVEC-L grown in 12-well plates were incubated in KRBH for 30 minutes at 37oC in the presence or absence of 0.2 mM Rp-8CPT-cAMPS (Rp). Then, 100 μM IBMX (I), 1 μM DDAVP, 10 μM forskolin (Forsk), or 0.5 U/mL thrombin (Thr) were added and the incubation continued for 30 minutes. Results are expressed in relative values, release from control cells being defined as 100%. The vWF released during the preincubation was subtracted, assuming continuous basal release over 1 hour. Data are the mean ± SEM of five experiments. (AP < 0.02 by Student’s paired t test).