Arachidonic acid-induced aggregation of platelets from human cord blood compared with platelets from adults

Using a double-sample technique, platelet aggregation induced by arachidonic acid (AA) was studied in cord blood samples from 29 newborns and 20 adults, all healthy and drug-free. Of the platelets from adults (10 males, 10 females), all aggregated after 1.0 mM AA. After 0.5 mM AA, all platelets aggregated except those from 4 males which did not respond at all. The great majority of cord blood samples aggregated similarly to samples from adults. Platelets from all 15 newborn females and 11 of 14 newborn males aggregated irreversibly after 1.0 mM AA, while those from 3 of the 14 male newborns showed a reversible aggregation. All 11 newborn samples aggregated irreversibly after 0.5 mM AA. These results prove that the cyclo-oxygenase pathway for platelet aggregation operates satisfactorily in newborn infants. The double-sample technique is of value for cord blood samples. Late cord blood samples showed more marked aggregation than samples taken earlier.