Sodium intake as a determinant of urinary prostaglandin E2 excretion

The effect of salt-loading on urinary prostaglandin D2 (PGE2) was studied in the rat. PGE2 doubled after 4 days of gavage with 40 ml 0.9% saline. Control animals receiving 5% glucose or tap water did not show this increase. When rats were allowed ad lib saline, PGE2 increased after 2 weeks, but returned to normal at 5 weeks. This same phenomenon of increased PGE2 early in the course of salt-loading was also observed in Dahl salt-sensitive and salt-resistant rats fed an 8% salt diet. Inhibition of prostaglandin biosynthesis by meclofenamate or indomethacin did not attenuate the natriuretic effect of saline loading. We conclude: 1) Salt-related changes in PGE2 is a time-dependent phenomenon, and 2) PGE2 is not the natriuretic factor since levels normalize despite continued salt-loading, and natriuresis was unaffected by prostaglandin blockade.