Urinary excretion of arterial blood prostaglandins and thromboxanes in man

Abstract

To determine the fraction of the arterial prostaglandin E2 (PGE2), 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), and thromboxane B2 (TXB2) that is excreted unmetabolized into human urine, the 3H-labeled compounds were separately infused into the renal artery or brachial vein of 23 subjects. Urine extracts were subjected to sequential chromatography on thin-layer plates, Sephadex LH-20, and reverse-phase high-pressure liquid chromatography to isolate the unmetabolized fraction. Dual isotope ratio techniques were used to identify peak fractions, to assess purity, and to calculate recovery. Following renal artery infusions, 32.2% of 6-keto-PGF1 alpha, 13.5% of TXB2, and 3.9% of PGE2 were excreted unmetabolized. Calculated fractional excretion of these compounds on a single transit through the kidney are approximately 30, 13, and 3.9%, respectively. Following brachial vein infusion of [3H]prostaglandin I2, 2.7% of the infusate was excreted as 6-keto-PGF1 alpha, suggesting that circulating prostaglandin I2 may contribute to urinary 6-keto-PGF1 alpha. When combined with published measurements of urinary PGE2, 6-keto-PGF1 alpha, and TXB2, these data can be used to calculate the maximum arterial blood concentration of these substances. The results indicate that arterial blood concentration of PGE2, TXB2, and 6-keto-PGF1 alpha in man are only a few picograms per milliliter or less.