A new automated technique for platelet aggregation measurement

Platelet-derived growth factor release and antiplatelet treatment with low-dose acetylsalicylic acid

Platelet-derived growth factor (PDGF) and beta-thromboglobulin (beta-TG) are released from alpha granules during platelet activation. PDGF may play a role in the development of atherosclerosis and the late restenosis after percutaneous transluminal coronary angioplasty (PTCA). The effect of acetylsalicylic acid (ASA) on PDGF release was studied in healthy volunteers before and twelve hours after ingestion of 300 mg ASA. PDGF, beta-TG, and thromboxane B2(TxB2) were measured by radioimmunoassay (RIA) in serum and in platelet rich plasma (PRP) after submaximal stimulation with collagen. TxB2 decreased significantly from 0.9 +/- 0.3 ng/(mL x 10(6) platelets) to 0.006 +/- 0.005 ng/(mL x 10(6) platelets) (mean +/- SD) in serum after ASA ingestion while PDGF and beta-TG remained unchanged. Measurements in PRP after stimulation with collagen showed a significant decrease in PDGF (from 21.5 +/- 1.4 pg/(mL x 10(6) platelets) to 1.8 +/- 4.1 (pg/mL x 10(6) platelets), in beta-TG (from 21.0 +/- 13.3 ng/(mL x 10(6) platelets) to 2.2 +/- 1.4 ng/(mL x 10(6) platelets)) and in TxB2 (from 143.6 +/- 80.7 pg/(mL x 10(6) platelets) to 0.5 +/- 0.6 pg/(mL x 10(6) platelets)) after treatment with ASA. In conclusion low-dose ASA inhibits collagen-induced release of both beta-TG and PDGF in PRP and TxB2-synthesis in PRP and serum.

Acetylsalicylic acid 100 mg and 1000 mg daily in acute myocardial infarction suspects: a placebo-controlled trial

Of 1078 patients admitted to the coronary care unit with acute chest pain, 293 who had possible acute myocardial infarction and symptoms of median 4 h duration were randomized to treatment with acetylsalicylic acid (ASA) 100 mg daily, 1000 mg daily or placebo for 3 months. During hospitalization, the combined incidence of cardiac death and non-fatal myocardial infarction on-treatment (withdrawals not included) was significantly lower (P less than 0.02) in the 100 mg group (7.1%) than in both the 1000 mg group (20.8%) and the placebo group (19.7%). During later time periods of treatment and at all time periods analysed according to the intention-to-treat principle (withdrawals included), data suggested the same trend, but differences were not statistically significant. Collagen-induced platelet aggregation and serum thromboxane B2 were reduced to the same degree in the two ASA groups and were normal in the placebo group. The data suggest that low-dose ASA could be cheap and safe as first-aid therapy in myocardial infarction suspects.

Antithrombin III activity, von Willebrand factor antigen and platelet function in young diabetic patients treated with multiple insulin injections versus insulin pump treatment

In a prospective study with cross-over design 20 patients with insulin-dependent diabetes mellitus of more than 2 years duration were treated for 6 months with continuous subcutaneous insulin infusion (CSII) and multiple insulin injections (MII). Metabolic control, platelet aggregability, thromboxane B2 levels in serum and plasma as well as antithrombin III (ATIII) activity and von Willebrand factor antigen were evaluated. A good metabolic control was obtained by both intensified regimens. No difference could be demonstrated between either platelet function tests or serum level of von Willebrand factor antigen during treatment with CSII and MII. However, the plasma level of ATIII activity was significantly higher (P less than 0.01) during MII treatment as compared to CSII treatment. There was no correlation between ATIII activity and daily insulin requirement or serum fructosamine. In conclusion, long-term metabolic control with MII has a favourable effect on ATIII activity in plasma. This may be important for a delay in onset and progression of diabetic vascular complications.

A computerized multichannel platelet aggregometer system

Commercially available instrumentation for conducting platelet aggregation studies in clinical and research laboratories consists of one-, two-, or four-channel aggregometers used in conjunction with strip chart recorders. These instruments have limited utility in large-scale drug screening and evaluation of the mode of action of drugs or in the clinical diagnosis of platelet disorders. A new instrument, a computerized multichannel aggregometer system (CMPAS) has been developed to collect, display, and analyze platelet aggregation data. The system is comprised of a 24-channel Born-type aggregometer, interfaced to a Rockwell AIM-65 microcomputer through an analogue-to-digital converter and an Epson dot-matrix printer. Each channel is individually calibrated, and aggregation data can be collected on up to 24 different platelet-rich plasma samples simultaneously. Conversational programs written in BASIC prompt the user for the addition of agonists and inhibitors. The tracings for each channel are displayed simultaneously, and a program automatically analyzes the data to generate the following parameters: baseline optical density, maximum aggregation response, positive and negative slopes, time to peak aggregation, and percentage response. Computerized multichannel aggregometer system data outputs are comparable to data generated by a standard Chronolog aggregometer unit. The advantages of the system include multichannel capability, simultaneous display of all channels allowing relative comparisons between control and experimental groups, and time savings and improved efficiency in conducting and analyzing aggregation experiments.