Influence of mental stress on plasma level of prostaglandins, thromboxane B2 and on circulating platelet aggregates in man.

In two groups of medical students (group A n=13, group B n=9, aged 23 to 28 years) we estimated the levels of PGE, PGF2 alpha, 6-keto-PGF1 alpha and thromboxane(TX)B2 by means of radioimmunoassay in the peripheral venous blood immediately before (BES) and 15-30 min after (AES) examination stress and compared these to control levels. Furthermore we determined the circulating platelet aggregates, the heart rate and blood pressure changes. Heart rate and systolic blood pressure increased in the BES period expressing a stressful situation. In BES the plasma level of PGE increased from 84 to 249 pg/ml (p less than 0.001), whereas PGF2 alpha was unchanged. The increase of PGE level seems to be an expression of the increased sympathetic nervous activity existing in the stressful situation. The level of 6-keto-PGF1 alpha, the stable metabolite of prostacyclin, behaved differently in the two groups. In group A there was a statistically significant increase (p less than 0.05), whereas in group B the 6-keto-PGF1 alpha level was unchanged. In AES the TXB2 level increased from 113 to 167 pg/ml (p less than 0.01), whereas under BES conditions the TXB2 level was not changed. Simultaneously with the increased TXB2 level the circulating platelet aggregates were increased. The increase in TXB2 level occurring only after the end of the examination may offer a possible explanation of the frequent appearance of heart attacks after stressful situations.