Distribution of arachidonic acid and other fatty acids in the lipids of guinea-pig uterus and plasma in relation to uterine prostaglandin synthesis.

Prostaglandin precursor fatty acids, predominantly arachidonic acid, were found in the different lipid classes of guinea-pig uterus and plasma on Days 7 and 15 of the oestrous cycle. Of the total arachidonic acid in the uterus, 93% was esterified to uterine phospholipids, of which 80% was bound to phosphatidylcholine and phosphatidylethanolamine. There was a significant decrease in the quantity of arachidonic acid bound to phosphatidylcholine between Days 7 and 15 of the oestrous cycle. Less than 0.1% of the uterine arachidonic acid was present in the unesterified form. It is suggested that phosphatidylcholine may form the source of phosphatidyl for uterine prostaglandin synthesis in the guinea-pig.