Evidence for an extra-renal origin of urinary prostaglandin E2 in healthy men

In order to verify the validity of the assumption that male urinary Prostaglandin (PG) E2 reflects its renal production, PGE2 and PGF2 alpha concentrations were measured by radioimmunoassay in the renal venous plasma (RVP) and urine (U) of 12 male and 4 female healthy volunteers. While women had a similar PGE2/PFG2 alpha ratio in RVP (0.59 +/- 0.18) and U (0.41 + 0.06), men and a significantly (P less than 0.05) higher ratio in U (1.43 +/- 1.72) as compared to RVP (0.54 +/- 0.16). This was largely due to considerably higher and more variable U-PGE1 concentrations (roughly 6 times higher than female values), despite almost identical RVP levels. The possibility of an increased U excretion of a cross-reacting member of the PG-system, as a cause of such apparently high PGE2-like immunoreactivity (LI), was ruled out by TLC characterization of PGE2-LI with three different anti-PGE1 sera. Thus, male U-PGE2 may variably reflect an extra-renal source, such as contamination with trace amounts of seminal fluid. It is concluded that, unless such a contamination can be monitored and corrected for, measurement of male U-PGE1 should be considered of questionable relevance to renal PG-synthesis.