Determination of 2,3-dinor-6-ketoprostaglandin F1 alpha in urine samples by liquid chromatography and radioimmunoassay

A bradykinin antagonist inhibited nitric oxide generation and thromboxane biosynthesis in acute pancreatitis

The effect of bradykinin on nitric oxide generation and eicosanoid production in the early stage of an experimental model of acute necrotizing pancreatitis induced by sodium taurocholate has been evaluated. We have compared the effect of administering a long-acting bradykinin antagonist, HOE 140, and an inhibitor of nitric oxide synthase, NG-nitro-L-arginine methyl esther L-NAME) on pancreatic prostanoid synthesis. Plasma lipase levels were increased after acute pancreatitis induction, and reduced after HOE 140 or L-NAME administration. Nitric oxide production and thromboxane B2 levels were increased after pancreatitis induction and the increases were reduced by L-NAME or HOE 140 administration. In contrast, increased prostacyclin production, reflected as 6-keto-PGF1 alpha levels, was not modified by L-NAME or HOE 140. Bradykinin seems to be involved in nitric oxide and thromboxane synthesis during the initial phases of acute necrohemorrhagic pancreatitis.

Application of an alpha-sidechain length-specific monoclonal antibody to immunoaffinity purification and enzyme immunoassay of 2,3-dinor-6-keto-prostaglandin F1 alpha from human urine

2,3-Dinor-6-keto-prostaglandin F1 alpha (2,3-dinor-6-keto-PGF1 alpha) is a major urinary metabolite of PGI2 (prostacyclin) and one of the most reliable parameters of PGI2 production in vivo. A mouse was immunized with 2,3-dinor-6-keto-20-carboxy-PGF1 alpha conjugated to bovine serum albumin for preparation of a monoclonal antibody which recognized the difference in the alpha-sidechain length of 6-keto-PGF1 alpha and its 2,3-dinor-metabolite. A sensitive and specific enzyme immunoassay was developed by the solid-phase competition method with 2,3-dinor-6-keto-20-carboxy-PGF1 alpha labeled with peroxidase protein. The detection range of the assay was 14-1200 fmol (IC50 = 120 fmol). The cross-reactivities of the antibody with 6-keto-PGF1 alpha, 6,15-diketo-13,14-dihydro-PGF1 alpha, and other arachidonate metabolites were less than 0.01%. An immunoaffinity column was prepared by coupling the anti-2,3-dinor-6-keto-PGF1 alpha antibody to BrCN-activated Sepharose 4B. Human urine was applied to an octadecylsilyl silica cartridge, and the extract was applied to the immunoaffinity column. This procedure allowed an efficient separation of 2,3-dinor-6-keto-PGF1 alpha from unidentified urinary substances which interfered with immunoassay. Validity of the results obtained by the enzyme immunoassay was confirmed by GC/MS employing selected ion monitoring for quantification.

The effect of acetaminophen on prostacyclin production in pregnant women

OBJECTIVE

The purpose of this study was to determine if acetaminophen decreased prostacyclin production by endothelial cells in culture and by pregnant women.

STUDY DESIGN

The effect of acetaminophen on endothelial cells in culture was determined by the addition of acetaminophen in concentrations of 10 and 100 micrograms/ml with comparison to control and indomethacin at 10 micrograms/ml. Prostacyclin production was estimated in 24 and thromboxane A2 production in six third-trimester pregnant women by measurement of excretion of urinary metabolites before and after ingestion of either 1000 mg of acetaminophen or placebo.

RESULTS

Compared with control (549 +/- 61 pg/well, mean +/- SD), production of prostacyclin in vitro was significantly inhibited by acetaminophen at 10 micrograms/ml (321 +/- 25) and 100 micrograms/ml (257 +/- 14). This inhibition is similar to inhibition by 10 micrograms/ml of indomethacin (228 +/- 11). Excretion of prostacyclin metabolite was significantly lower after ingestion of acetaminophen (2233 +/- 446 vs 1246 +/- 199 pg/mg creatinine, mean +/- SEM) but unchanged after ingestion of placebo (1745 +/- 304 vs 1712 +/- 211). There was no difference in response between normal and hypertensive women, and there was no effect of acetaminophen on thromboxane metabolite excretion.

CONCLUSION

Acetaminophen in typical oral doses results in reduced production of prostacyclin by endothelial cells in culture and in a reduction in prostacyclin, but not thromboxane, production in pregnant women.

Altered levels of tissue and urinary prostacyclin in rats subjected to pancreas transplantation

Significant increases of TXB2 and PGE2 are reported to occur in pancreas transplantation. These increases are prevented with scavengers of oxygen-free radicals. In this communication, we report on changes of prostacyclin metabolites such as tissue 6-keto prostaglandin F1 alpha and urinary 2,3-dinor 6-keto prostaglandin F1 alpha in rats subjected to pancreas transplantation after different periods of organ cold preservation ischemia as well as the effect of superoxide dismutase (SOD) on these changes. For this purpose, male Lewis rats were classified as follows: Group I, Control; Group II, syngenic pancreas transplantation after 15 min of organ preservation in Collins solution at 4 degrees C; Group III, same as II but with 12 hours of organ preservation; Group IV, same as III, but with SOD pretreatment. Results have shown significant posttransplantation increases of both tissue 6-keto PGF1 alpha and urinary 2, 3 dinor 6-keto PGF1 alpha, the latter being a useful marker to evaluate systemic prostacyclin (PGI2) production by rat pancreas. This effect was prevented when the organ had been exposed to SOD during the period of cold preservation ischemia. These results confirm the implication of oxygen-free radicals (OFR) in the ischemia-reperfusion process associated to rat pancreas transplantation leading to enhanced arachidonic acid metabolism.

The effect of magnesium sulfate infusion on systemic and renal prostacyclin production

Recent in vitro studies have suggested that magnesium sulfate (MgSO4) infusions may increase prostacyclin production. We studied the effect of MgSO4 infusion on prostacyclin (PGI2) metabolite excretion in women with either pregnancy induced hypertension or preterm labor. Excretion of renal and systemic metabolites of PGI2 was measured prior to and following the start of MgSO4 infusion in the two groups. An increased in renal PGI2 metabolite preterm labor excretion was noted in the hypertension group but no change was noted in systemic PGI2 excretion in either group. These data fail to support a generalized, short term increase in endothelial cell PGI2 production as the basis for the beneficial effect of MgSO4.

Modern high-performance liquid chromatographic-radioimmunoassay strategies for the study of eicosanoids in biological samples

An evaluation of the most recent literature on the determination of eicosanoids by immunoassay methods confirms that owing to the inherent lack of specificity of many of the antibodies used for this purpose, immunological assays (radioimmunoassay or enzyme immunoassay) are often preceded by solid-phase extraction followed by further purification of the antigens of interest by routine reversed-phase high-performance liquid chromatographic methods. In this way the analytical potential of radioimmunoassay is remarkably enhanced and accuracy and precision of the assay are ensured.