A facile reproducible radioimmunoassay of the mixed metabolites of prostaglandins E, suitable for measurement of relative differences of phospholipase/prostaglandin synthetase activity in vivo.

A relatively simple, reproducible, radioimmunoassay for the mixed metabolites of prostaglandins E (U-PGE-M) in rat and human urine is described. Results of the assay of treated versus control urine extracts correlate well with differences expected from treatments known to alter in vivo phospholipase/prostaglandin synthetase activity. Cross-reactivity of heterogeneous metabolite antiserum with 5 available endogenous prostaglandins and a single metabolite was determined and showed little or no cross reaction. Sensitivity, within-assay precision, interassay reproducibility, and parallelism were also determined and found acceptable. Excretion rates of U-PGE-M by rats and humans were determined, and statistically significant differences could be shown, although absolute values were smaller than estimated absolute values obtained from mass-spectrometric measurements of single, purified metabolites. Normal human male excretion rates differed significantly from those of females. Injection of prostaglandin E1 caused a significant rise in U-PGE-M excretion in rats whereas aspirin and indomethacin caused it to fall. U-PGE-M excretion rates of spontaneous hypertensive rats were significantly less than rates of normotensive controls. Adrenalectomy resulted in excretion of significantly larger amounts of U-PGE-M than in normal or sham-operated controls. A screen of clinically active pharmacological agents and hormones gave results consistent with previously published reports.