The effect of regular and enteric-coated aspirin on bleeding time, thromboxane, and prostacyclin

We compared the effect of different aspirin schedules, dosages, and formulations on various bleeding time parameters including bleeding time, plasma and total blood volume, and levels of the stable metabolites of thromboxane A2 (TXA2) and prostacyclin (PGI2) (respectively, TXB2 and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha)) to determine the optimal dosage and formulation of aspirin to inhibit TXA2 production while sparing PGI2. In a randomized, parallel study, 52 healthy male volunteers (62 independent observations) with no history of bleeding disorders were given 80 mg or 325 mg of regular aspirin, or 325 mg of enteric-coated aspirin to ingest daily (14 pills) or every other day (7 pills) for a continuous 14 day period. Bleeding times were performed on day 1 before aspirin, 6 h after aspirin on day 1, and before aspirin on day 14. Bleeding times, plasma volume, and total volume increased significantly from before aspirin to after 6 h and 14 days (p < 0.0001 for all parameters) for all aspirin formulations. For day 1 before aspirin ingestion to 6 h later, both TX and PGI2 (p < 0.008) decreased significantly. 6 h after ingestion of aspirin on day 1 to day 14, both TX and PGI2 levels also significantly decreased (p < 0.0001). There was a highly significant decrease in PGI2 production on every other day aspirin schedules (p = 0.0001) particularly with 80 mg of aspirin, while the decrease in PGI2 production on daily aspirin was not significant (p = 0.10). The most favourable ratio of 6-keto-PGF1 alpha to TXB2 occurred with 80 mg daily.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid ultrastructural changes in the dense tubular system following platelet activation

The dense tubular system (DTS) functions to regulate platelet activation by sequestering or releasing calcium, similar to the sarcotubules of skeletal muscle. In resting platelets, the DTS exists as thin elongated membranes. Within 10 seconds of the addition of thrombin, platelets show a major ultrastructural change in their DTS: from the thin elongated form to a rounded vesicular form. These morphologic changes were demonstrated with two different stains and two different fixation methods. Platelets exposed to the calcium ionophore A23187 showed the same ultrastructural changes in the DTS. In contrast, the DTS remains in a thin elongated form when platelets are stimulated by the protein kinase C activators phorbol 12-myristate 13-acetate (PMA) and oleoylacetylglycerol (OAG). These morphologic changes may be related to the discharge of calcium from the DTS because this is stimulated by thrombin and A23187, but not by PMA. Preincubation of the platelets with the intracellular calcium chelator 5,5'-dimethyl-bis-(0-aminophenoxy)-ethane-N,N,N',N tetra acetic acid (BAPTA) largely prevented both the thrombin-induced rise in intracellular calcium and the changes in DTS morphology, suggesting that the changes in DTS morphology are secondary to the increase in cytosolic calcium. The results provide a morphologic correlate to existing biochemical evidence showing that the DTS is involved early during paltelet activation.

Dietary omega 3 fatty acids and gestational hypertension in the Inuit

Blood pressure at the end of pregnancy and the incidence of pregnancy-induced hypertension were monitored in Inuit communities in the Keewatin region of the Northwest Territories. Communities with more fish and sea mammals in their diet had a lower blood pressure at the end of pregnancy and a lower incidence of gestational hypertension. The lower incidence of gestational hypertension was independent of other variables, including pregravida weight and parity. Cord blood phospholipid fatty acid analysis confirmed higher levels of eicosapentanoic acid, a fatty acid enriched in fish and sea mammals, in infants born to mothers from communities with higher fish in their diets.