Intracellular calcium oscillations in dA1VWF-adherent platelets. As described in “Materials and methods,” washed platelets loaded with Oregon Green and Fura Red were plated onto coverslips coated with dA1VWF in the presence of inhibitors of signaling through αIIbβ3 and ADP and thromboxane A₂ receptors. After 5 minutes, confocal images were acquired serially and (Ca²⁺)i was quantified for individual platelets. (A) Typical (Ca²⁺)i changes occurring in most platelets showed oscillations either just over baseline (low) () or within an intermediate range (mid) (▴, ▪). (B) Approximately 15% of platelets showed more sustained, high-amplitude calcium oscillations reaching several μM (high). Results are representative of 10 separate experiments. (C) dA1VWF-dependent changes in (Ca²⁺)i are regulated by cyclic AMP and Ca²⁺ influx. Platelets were allowed to adhere to dA1VWF in the presence of 400 μM c-BIMPS to increase cyclic AMP or 5 mM EDTA to block Ca²⁺ influx. Results are expressed as a percent of the dA1VWF-mediated response in the absence of these 2 inhibitors. Data represent means ± SEM of 3 experiments.