Effect of forskolin on adhesion of K562-GPIb/V/IX cells to VWF under flow, sensitivity to RAM.1 treatment.

Adhesion of K562-GPIb/V/IX and K562-GPIb(βSer166Gly)/V/IX cells to microcapillaries coated with bovine VWF was followed for 10 minutes at a shear rate of 150 s^-1. Adherent cells were counted off-line at the indicated times. (A) Cells were left untreated (■) or incubated for one hour at 37°C with 10 μM () or 50 μM (□) forskolin (Fsk). (B) Cells incubated or not with 50 μM forskolin were further incubated for 10 minutes with 10 μg/mL RAM.1 or control rat IgG1 and perfused through bovine VWF-coated capillaries. Results are expressed as the mean ± SEM of 3 separate experiments; * P < .05, **P < .01. Treatment with forskolin significantly increased adhesion of cells transfected with the wild-type complex (P < .05), but had no effect on the adhesion of GPIb(βSer166Gly) mutant cells. In K562-GPIb/V/IX cells, RAM.1 treatment abolished the effect of forskolin.