Effect of EDTA and PGE1 on beta-thromboglobulin liberation from platelets

Platelet function and exercise-induced myocardial ischaemia in coronary heart disease patients

Divergent reports of the effects of exercise-induced myocardial ischaemia on platelet function require clarification. This study examines the relationship between exercise, exertional myocardial ischaemia, and in vivo and ex vivo platelet function in 27 male patients, aged 35 to 69, with stable coronary heart disease (CHD). All medications were ceased at least 5 days prior to a maximal exercise test. Blood was sampled before and after exercise to measure plasma and serum thromboxane B2 (TXB2), plasma beta-thromboglobulin (BTG), platelet count ratio (PCR), platelet count (PC), haemoglobin (Hb), haematocrit (Hct) and white cell count (WCC). The exercise test and blood measurements were repeated 5 weeks later, under the same conditions to confirm the reproducibility of any changes. Thirteen patients had a positive test for ischaemia and 14 a negative test. The PC, Hb, Hct and WCC increased in all patients after exercise, confirming earlier reports. The BTG level increased (25 +/- 9 to 30 +/- 15 ng/ml, p less than 0.05; and 24 +/- 9 to 32 +/- 8 ng/ml, p less than 0.004 in the repeat test) and was unrelated to exertional ischaemia. A decrease in the PCR only occurred in the non-ischaemic group in the initial test (0.84 +/- 0.14 to 0.78 +/- 0.13, p less than 0.02) but was not reproducible (0.84 +/- 0.10 to 0.82 +/- 0.13). No change occurred in plasma TXB2 levels. Serum TXB2 increased after exercise in the ischaemic group (255 +/- 150 to 314 +/- 190 ng/ml, and 240 +/- 139 to 370 +/- 169 ng/ml, p less than 0.05) but not in the negative test group (467 +/- 255 to 441 +/- 174 ng/ml, and 421 +/- 299 to 464 +/- 297 ng/ml, p greater than 0.1). Serum TXB2 discriminated poorly between individuals with positive and negative exercise tests. Thus, stable exertional ischaemia does not activate circulating platelets nor is it associated a priori with activated platelets. It may be associated with an increase in maximum thromboxane A2 production capability. Brief strenuous exercise may activate platelets in CHD patients independent of exertional ischaemia.

Low and high risk coronary patients discriminated by blood platelet fatty acid composition

The distribution of 11 long-chain fatty acids in platelet phospholipids were subjected to multivariate statistical analysis with groups of high and low risk coronary patients and controls. The alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) had significant explanatory power between the groups. As has been anticipated from studies in Eskimos, the EPA fraction was low in coronary patients. It was lower in high risk patients than in low risk patients, and lower in patients below rather than above, 60 years of age. Young high risk patients had 1.2 +/- 0.2% (Mean, SE) EPA against 1.8 +/- 0.2% in young controls, (p = 0.035). Old low risk patients had the highest EPA and also the highest DHA, 2.9 +/- 0.3% against 2.3 +/- 0.2% in controls. The ALA was low in low risk patients. Patients with low platelet EPA and high serum cholesterol should be included in trials with EPA rich diets.

Platelet function in platelet concentrates and in whole blood

Platelet function was studied in CPD whole blood stored at 4 degrees C for one and three days and in platelet concentrates stored at room temperature for the same periods of time. Comparisons were made of platelet shape, nucleotide content, beta-thromboglobulin (beta TG) liberated during storage, and platelet aggregation in response to ADP, collagen, sodium arachidonate and ristocetin. It was found that in whole blood the shape of the platelets was less discoid than in platelet concentrates. However, platelet aggregation in response to ADP, collagen, and sodium arachidonate was preserved better in whole blood than in platelet concentrates. Platelet nucleotides were the same in whole blood as in platelet concentrates, but the plasma levels of beta TG were less in whole blood. The results show that as judged by aggregation, beta TG release and nucleotide content, platelets from whole blood were at least as functional as those from platelet concentrates. However, platelets from whole blood had lost their discoid shape, which suggests that they would have a short survival in the circulation.