Prostaglandin formation and platelet aggregation during fasting and linoleic acid intake

Prostaglandin formation, estimated by the determination of tetranorprostanedioic acid (TNPDA) in the urine, and platelet aggregation were investigated in seven healthy volunteers each day during fasting, and in three of them additionally during intake of carbohydrates (328 kcal/day) or safflor oil (328kcal, 20g linoleic acid). Monitoring TNPDA in 8-h fractions of the urine showed a reduction during the night (23.00-07.00) by 70% on the average. During Days 1 and 2 of fasting the amount of TNPDA in 24-h urine was the same as under a conventional diet. On Day 3, TNPDA decreased in all experimental subjects to 162 μg/day on the average and was not changed by carbohydrate intake. A linoleic acid intake of 20 g/day increased TNPDA in 24-h urine to pre-experimental levels measured under free diet. Platelet aggregation did not change during the experiment. No relationship between prostaglandin formation and lipolysis in man was found.