Species variation in serum levels of prostaglandins and their precursor acids

Levels of prostaglandin (PG) precursor acids, and PGE2, PGF2 alpha and TXB2 in sera of adult animals (5/species) were determined by gas chromatography and radioimmunoassay, respectively. The level of arachidonic acid in horse serum lipids was the lowest (0.61 +/- 0.03%), and that in dog serum lipids was the highest (18.1 +/- 1.8%). Bovine serum lipids contained considerable amounts of 20:3 omega 6 (precursor of monoene PG) and 20:5 omega 3 (precursor of triene PG) in addition to arachidonic acid. Thromboxane B2 was not the major species of endoperoxide metabolite synthesized by platelets from arachidonic acid in male ruminants and pig. The concentration of TXB2 in the serum of the lactating cow was more than 50 times greater than that of ovariectomized cows or of bulls. Although TXB2 was the major species of endoperoxide metabolite synthesized by human platelets, its serum concentration was much lower than that of nonruminant animals except the pig. These results showed that there were considerable variations in levels of PG and their precursors among various species of animals. The species variation in PG and TXB2 concentrations was not simply attributed to the differences in platelet concentration blood.