Fig 4.

Homocysteine stimulates Ca²⁺ entry and impairs Ca²⁺ mobilization by thrombin in platelets from healthy and diabetic donors. (A and B) Human platelets from healthy individuals (A) and diabetic patients (B) were suspended in HEPES-buffered saline (HBS) containing 1 mM Ca²⁺ and then exposed to increasing concentrations of homocysteine (Hcy; 50–200 μm). (C–F) Human platelets from healthy individuals (C and E) and diabetic patients (D and F) were suspended in a Ca²⁺-free medium (100 μm EGTA was added). Cells were treated (thick arrow) with either 0.1 U/ml thrombin (Thr; C and D) or with 10 μm ADP (E and F), in the absence or presence of 50, 100 or 200 μm Hcy, as indicated, and 4 min. later CaCl₂ (300 μm) was added to the medium to initiate Ca²⁺ entry. Traces are representative of 8–12 independent experiments.