IDENTIFICATION AND ASSAY OF TETRANOR-PROSTAGLANDIN-E1 IN HUMAN URINE

7.alpha.,11-Dihydroxy-5-keto-tetranorprost-9-enoic acid (tetranor-PGE1 [prostaglandin E1]) is a metabolite of PGE2 and PGE1 resulting from biotransformation only by .beta.-oxidation. The preparation of pentadeutero-tetranor-PGE1 is described, together with its use as a carrier-internal standard for the quantitative determination of tetranor-PGE1. The method employs addition of a known amount of deuterated standard to the sample and, after its isolation and derivatization, measurement of the ratio of protium and deuterium forms by GLC-mass spectrometry employing the technique of selected ion monitoring. Ratios of protium/D5-tetranor-PGE1 ranging from 0.006-0.084 (amount of the protium form per injection = approximately 0.3-4 ng) can be measured with a precision of .+-.6.5 to .+-.1.3% (SD), respectively, yielding a linear standard curve. Normal human females excreted tetranor-PGE1 in an average amount of 342 ng (.+-.116)/day. A mass spectrum of this metabolite isolated from urine confirmed its identity.