Inhibition of platelet aggregation by putrescine, spermidine, and spermine in hypercholesterolemic rabbits

Background. Hypercholesterolemia causes alterations in platelet function. Platelet hyper-aggregation is considered a predisposing factor for atherosclerosis. In this paper, the anti-aggregating effect of the polyamines putrescine, spermidine, and spermine was studied on platelets of normal and hypercholesterolemic rabbits. Methods. New Zealand rabbits were fed with a cholesterol-enriched diet for 10 weeks. Lipids and glucose were determined in serum. The assays of platelet aggregation were carried out using platelet-rich plasma (PRP) obtained from both control and cholesterol-fed rabbits. We used 2.5 mu mol/mL ADP and 2 mug/mL collagen as inductors of platelet aggregation. In addition, arginase activity and L-arginine content were determined in PRP. Results, Serum total cholesterol and LDL-cholesterol concentrations were increased from 26.3 +/- 8.1 to 1.485.0 +/- 26.8 mg/dL and from 15.9 +/- 5.9 to 1,383.8 +/- 58.9 mg/dL, respectively, whereas triglyceride concentration increased from 88.3 +/- 35.6 to 411.0 +/- 151.5 mg/dL upon cholesterol feeding. Seventy-five percent of platelet aggregation inhibition was observed with 10 muM of polyamines in PRP of normal rabbits. Spermine inhibited platelet aggregation by 54% in PRP of hypercholesterolemic rabbits when ADP was used as agonist. The order of polyamine action was spermine > spermidine > putrescine. In addition, we found that platelet arginase activity and L-arginine content were unaltered upon hypercholesterolemia. Conclusions. These results show that the polyamines putrescine, spermidine, and spermine have antagonist action in platelet aggregation and suggest a key role of polyamines in platelet aggregation under normal and hypercholesterolemic conditions. (C)2001 IMSS. Published by Elsevier Science Inc.