Effects of dietary essential fatty acid concentration upon prostanoid synthesis in rats

The effects of dietary linoleate as zero to 27% of energy, fed to female rats for 6 months, in relation to ability of whole blood to synthesize PG during clotting at 37 degrees was studied. Synthesis of PGE1, PGE2, PGF2 apha and TXB2 after 10 or 40 minutes of incubation of whole blood was determined by assay of serum concentration by radioimmunoassay. Fatty acid composition of serum phospholipids, cholesteryl esters and acyl glycerides was determined. PG synthesis increased with linoleate as zero to 2% of kcal; from 2% up to 7% there was a decrease of PG synthesis; from 7% to 27% there was a linear increase. There was no pattern to PGF2 alpha maximum concentration. PGE2 had a linear increase from 0 to 30% linoleate. PGE1 decreased with 0 to 2% linoleate, then increased between 2 and 7% and maintained a plateau through 27%. The concentration of TXB2 was found to be about 20-40 times that of PGE2 and PGF2 alpha. The decline of PGE1 synthesis with 2-7% linoleate calories was correlated with 20:3n-6 concentration and PGE2 and PGF2 alpha production with 20:4. With dietary linoleate concentrations greater than 7.4% PG synthesis had a linear increase up to 27% of kilocalories, not correlated with fatty acids.