Changes in urinary 6-keto-prostaglandin F1 alpha excretion during pregnancy and labor

Prostaglandins in biofluids in pregnancy and labour: A systematic review

Prostaglandins are thought to be important mediators in the initiation of human labour, however the evidence supporting this is not entirely clear. Determining how, and which, prostaglandins change during pregnancy and labour may provide insight into mechanisms governing labour initiation and the potential to predict timing of labour onset. The current study systematically searched the existing scientific literature to determine how biofluid levels of prostaglandins change throughout pregnancy before and during labour, and whether prostaglandins and/or their metabolites may be useful for prediction of labour. The databases EMBASE and MEDLINE were searched for English-language articles on prostaglandins measured in plasma, serum, amniotic fluid, or urine during pregnancy and/or spontaneous labour. Studies were assessed for quality and risk of bias and a qualitative summary of included studies was generated. Our review identified 83 studies published between 1968-2021 that met the inclusion criteria. As measured in amniotic fluid, levels of PGE2, along with PGF2α and its metabolite 13,14-dihydro-15-keto-PGF2α were reported higher in labour compared to non-labour. In blood, only 13,14-dihydro-15-keto-PGF2α was reported higher in labour. Additionally, PGF2α, PGF1α, and PGE2 were reported to increase in amniotic fluid as pregnancy progressed, though this pattern was not consistent in plasma. Overall, the evidence supporting changes in prostaglandin levels in these biofluids remains unclear. An important limitation is the lack of data on the complexity of the prostaglandin pathway outside of the PGE and PGF families. Future studies using new methodologies capable of co-assessing multiple prostaglandins and metabolites, in large, well-defined populations, will help provide more insight as to the identification of exactly which prostaglandins and/or metabolites consistently change with labour. Revisiting and revising our understanding of the prostaglandins may provide better targets for clinical monitoring of pregnancies. This study was supported by the Canadian Institutes of Health Research.

Urinary prostaglandin excretion in pregnancy: the effect of dietary sodium restriction

INTRODUCTION

Dietary sodium restriction results in activation of the renin-angiotensin-aldosterone-system. In the non-pregnant situation renin release in response to a low sodium diet is mediated by prostaglandins. We studied the effect of dietary sodium restriction on urinary prostaglandin metabolism in pregnancy.

PATIENTS AND METHODS

In a randomized, longitudinal study the excretion of urinary metabolites of prostacyclin (6-keto-PGF(1 alpha)and 2,3-dinor-6-keto-PGF(1 alpha)) and thromboxane A(2)(TxB(2)and 2,3-dinor-TxB(2)) was determined throughout pregnancy and post partum in 12 women on a low sodium diet and in 12 controls.

RESULTS

In pregnancy the excretion of all urinary prostaglandins is increased. The 6-keto-PGF(1 alpha)/ TxB(2)-ratio as well as the 2, 3-dinor-6-keto-PGF(1 alpha)/ 2,3-dinor-TxB(2)-ratio did not significantly change in pregnancy. CONCLUISION Prostacyclin and thromboxane do not seem to play an important role in sodium balance during pregnancy.

Which prostanoid metabolites should be determined for the study of reproductive processes?

The non-enzymatic metabolites of prostacyclin (PGI2) and thromboxane A2 (TXA2), 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha) and thromboxane B2 (TXB2), and their 2,3-dinor metabolites, 2,3-dinor-6-keto-PGF1alpha and 2,3-dinor-TXB2, were measured in early morning urine samples in 24 in vitro fertilization (IVF) cycles in 24 women and in 27 women who became pregnant after IVF and embryo transfer (ET). The sum of the non-enzymatic metabolites and their 2,3-dinor metabolites was considered to be a reflection of total PGI2 and total TXA2 production in vivo. Both the ratio of 'total' PGI2/'total' TXA2 and the ratio of the 2,3-dinor metabolites were calculated. TXB2 concentrations showed virtually no change and the ratios of the non-enzymatic metabolites of PGI2 and TXA2 versus their 2,3-dinor metabolites remained relatively constant. As a consequence, the ratio of 2,3-dinor-6-keto-PGF1alpha/2,3-dinor-TXB2 was a close reflection of the ratio of 'total' PGI2/'total' TXA2, although the latter ratio was significantly higher all the time. We conclude that for comparative studies on the balance between PGI2 and TXA2 in IVF cycles and during gestation, the determination of the 2,3-dinor metabolites alone can replace the measurement of all four metabolites.

Prostanoid excretion before in vitro fertilization relates to the likelihood of pregnancy

The objective of this study was to determine the urinary excretion of prostacyclin (PGI2) and thromboxane A2 (TXA2) metabolites during in vitro fertilization (IVF) in relation to the clinical outcome of IVF. Urine was obtained overnight every 3 to 4 days from 24 women during IVF cycles. TXB2, 6-keto-PGF1 alpha and their 2,3-dinor derivatives were measured by high-pressure liquid chromatography with radioimmunoassay. The patients were women with (n = 16, 119 samples) and without (n = 8, 53 samples) a clinical IVF pregnancy. Concentrations of 2,3-dinor-TXB2 and 2,3-dinor-6-keto-PGF1 alpha were lower before embryo transfer in women who achieved a pregnancy than in those who did not conceive (p < 0.05). Contrary to women who did not conceive, women who achieved pregnancy had an increase in 6-keto-PGF1 alpha excretion after embryo transfer (p = 0.04). In women who did not conceive, levels of 2,3-dinor-TXB2 were higher before embryo transfer than after transfer (p = 0.04) and than levels in women who did conceive (p = 0.01). We concluded that differences in urinary prostanoid metabolite excretion before embryo transfer appear to relate to the likelihood of pregnancy, but the nature of this relationship remains elusive.

Combining salicylate and enalapril in patients with coronary artery disease and heart failure

OBJECTIVE

To study the effects of adding a salicylate to the angiotensin converting enzyme inhibitor enalapril in patients with heart failure due to coronary artery disease.

DESIGN

Double blind, crossover study for three days in hospital followed by an extended similar study outside hospital over two months of once daily enalapril plus salicylate and enalapril plus placebo.

SETTING

Tertiary referral centre.

PATIENTS

20 patients with heart failure due to myocardial infarction (New York Heart Association class II or III) and an ejection fraction less than 0.40. Twelve patients completed the two parts of the study.

MAIN OUTCOME MEASURES

Blood pressure, plasma converting enzyme activity; plasma angiotensin II and noradrenaline concentrations; excretion of metabolites of renal and systemic prostanoids.

RESULTS

The unloading effect of first and second dose of enalapril in the morning lasted only during the day; in the extended study it lasted 24 hours because of the drug's accumulation. Converting enzyme inhibitors attenuate the breakdown of bradykinin and therefore enhance prostaglandin E2 synthesis mediated by bradykinin. Evidence was found of such a prostaglandin E2 mediated contribution to ventricular unloading by enalapril, which was blocked by salicylate. The contribution, however, was small and variable, and salicylate addition had on average no significant de-unloading effect during the day. Unloading was abolished in only three of the 20 patients in the short term study and in one of the 12 in the extended study. At night, when other effects of enalapril on blood pressure had waned and the bradykinin induced effect persisted, salicylate significantly reduced the remaining small unloading effect. No effect was seen of salicylate addition on reversal of remodelling. Enalapril reduced angiotensin II induced synthesis of systemic and renal prostaglandin I2 and thromboxane A2, initially only during the day, but later also at night. It thereby masked suppression of thromboxane A2 synthesis by salicylate, which is the effect to which reinfarct prevention by salicylate is attributed.

CONCLUSION

The risk is low that salicylate will substantially reduce the benefit of enalapril in patients with heart failure by de-unloading the ventricle. Like other effects induced by bradykinin significant de-unloading occurs in only a minority of the patients. In the presence of enalapril, however, salicylate will probably not be as effective as expected in reducing reinfarction risk, because enalapril already reduces thromboxane A2 synthesis effectively in patients with heart failure and no further reduction by salicylate was found.

Prostanoid levels in in vitro fertilization culture medium are not related to the likelihood of implantation

OBJECTIVE

To determine prostanoid levels (prostaglandin E2, prostaglandin F2 alpha, 6-keto-prostaglandin F1 alpha, and thromboxane B2 [TXB2]) in embryo culture medium containing inactivated maternal serum and their correlation with the clinical outcome of IVF-ET.

DESIGN

Prostanoid levels were measured in blank control medium and in medium containing an embryo or nonfertilized oocyte with a high-pressure liquid chromatography (HPLC-RIA) method. Comparisons of HPLC-RIA, Seppak C18-RIA, and RIA directly in the medium demonstrated identical results for TXB2, allowing the use of direct RIA in the large investigation of 129 media.

SETTING

Leiden University Hospital, The Netherlands.

PATIENTS

Patients with (n = 12) and without (n = 15) an ongoing pregnancy after IVF-ET.

MAIN OUTCOME MEASURES

Prostanoid levels in embryo culture medium and relationship between prostanoid levels and successful implantation.

RESULTS

Thromboxane B2 is the only prostanoid consistently found in these media. In both groups there was no difference in TXB2 levels between control media, media containing a nonfertilized oocyte, and media containing an embryo. There was no difference in TXB2 levels between media that had harbored the beginning of a successful pregnancy and those that had not produced a pregnancy.

CONCLUSION

Thromboxane B2 in the embryo culture medium originates from maternal serum and bears no relationship with the likelihood of fertilization and implantation.

Excretion of prostacyclin and thromboxane metabolites before, during, and after pregnancy-induced hypertension

The aim of the present study was to assess whether changes in prostacyclin (PGI2) and thromboxane (TXA2) generation precede the manifestation of pregnancy-induced hypertension (PH). The metabolites 6-oxo-PGF1 alpha and TXB2 were measured in the urine of 69 randomly selected pregnant women from 16-20 weeks of gestation (wg) until delivery and more than 6 weeks postpartum. Between 16-20 and 21-24 wg 6-oxo-PGF1 alpha excretion did not change in patients who later developed PIH (n = 6) but increased significantly in the control group (n = 63). In contrast, a marked rise in TXB2 excretion was found in the PIH group but not in controls. Thereafter significant differences between both groups persisted from 25 wg until delivery. The 6-oxo-PGF1 alpha/TXB2 ratio was below the 10th percentile from 21-24 wg until delivery in patients with developing PIH. The excretion of both metabolites was substantially lower in the non-pregnant state without any difference between patient groups. These results show an altered urinary excretion of both 6-oxo-PGF1 alpha and TXB2 preceding the onset of the disease. A pathophysiological role of PGI2 deficiency and increased TXA2 formation in PIH appears substantiated.

Secretory diarrhea in villous adenoma of rectum: effect of treatment with somatostatin and indomethacin

The effects of treatment with the synthetic long-acting somatostatin analogue SMS-201-995 were studied in a patient with a fluid and electrolyte secreting villous adenoma of the rectum. The effects of SMS-201-995 on rectal fluid volume and electrolyte loss, and local and general prostanoid production were compared with those of treatment with indomethacin. During treatment with the somatostatin analogue iso-osmolar rectal fluid production increased about 25%; the quantity of prostaglandin E2 in the rectal fluid rose almost 20-fold. Prostaglandin F2 alpha, 6-keto-prostaglandin F1 alpha and 13,14-dihydro-15-keto-prostaglandin F2 alpha output showed similar, though less impressive increments during somatostatin treatment. The somatostatin analogue did not affect urinary prostanoid excretion except for levels of 2,3-dinor-thromboxane B2, which doubled. With indomethacin treatment diurnal rectal fluid production dropped by about 50% and all prostanoids measured in urine and rectal fluid decreased below control values. It appears that the somatostatin analogue SMS-201-995 has a marked stimulatory effect on the in vivo prostanoid production by the villous adenoma. Perhaps this stimulation is not confined to the tumor only, but also affects thromboxane synthesis.

Simultaneous measurements of prostacyclin and thromboxane metabolites during the menstrual cycle

The balance between prostacyclin and thromboxane is known to be important for reproductive and cardiovascular health but has been difficult to quantify. Whereas their stable urinary metabolites, 6-keto-prostaglandin F1 alpha and thromboxane B2, may reflect in part systemic changes, it has been suggested that 2,3-dinor-6-keto-prostaglandin F1 alpha and 11-dehydro-thromboxane B2 more adequately reflect systemic production. Therefore we report for the first time the simultaneous measurements of 6-keto-prostaglandin F1 alpha, thromboxane B2, 2,3-dinor-6-keto-prostaglandin F1 alpha, and 11-dehydro-thromboxane B2 during the menstrual cycle. Timed urine collections were obtained from 18 ovulatory women, aged 22 to 40, during the midfollicular and midluteal phases. Serum estradiol, progesterone, urinary pregnanediol glucuronide, estrone glucuronide, and creatinine also were measured. Prostanoid extraction from urine by C18 and silica Bond Elut columns were then separated by high-performance liquid chromatography before radioimmunoassay. Concentrations of all urinary prostanoids were not significantly different in the follicular phase when compared with the luteal phase. A positive correlation of borderline significance was noted between luteal thromboxane B2 and pregnanediol glucuronide (r = 0.70) and between luteal estrone glucuronide and 2,3-dinor-6-keto-prostaglandin F1 alpha (r = 0.68). A significant correlation was found between follicular estrone glucuronide and the 6-keto-prostaglandin F1 alpha/11-dehydro-thromboxane B2 ratio (r = 0.83, p less than 0.04). These novel normative data suggest an influence of sex steroids on prostacyclin and thromboxane metabolism.

Prostacyclin versus thromboxane metabolite excretion: changes in pregnancy and labor

Urinary TXB2 and 6-keto-PGF1 alpha were measured by high pressure liquid chromatography combined with radioimmunoassay, in order to determine whether or not urinary excretion of 6-keto-PGF1 alpha and TXB2 followed a same pattern in pregnancy and labor. The excretion of 6-keto-PGF1 alpha was higher than that of TXB2 in both non-pregnant and pregnant women, but the ratio between them increased in pregnancy. The urinary excretion of both 6-keto-PGF1 alpha and TXB2 excretion was significantly increased (p less than 0.001) in pregnancy. Labor was associated with a much wider inter-individual variation in the excretion of 6-keto-PGF1 alpha and TXB2 than observed in pregnancy and in non-pregnant women. Also, the ratio between the two compounds varied more in labor than in pregnancy. The data indicate that the urinary levels of these two compounds do not follow a single well-determined pattern in pregnancy and labor.

Extraction with methyl tert-butyl ether overcomes erratic elution patterns of 6-keto-prostaglandin F1 alpha on high pressure liquid chromatography

Solvent extraction of 6-keto-PGF1 alpha from aqueous solutions with ethyl acetate was found to result in variable and irreproducible elution patterns, when the extracts were subjected to high pressure liquid chromatography. These problems could not be resolved satisfactorily by using ethyl acetate from different suppliers, nor by changing acids or pH for acidification. After a number of unsuccessful attempts to resolve this problem, we found that variable and irreproducible elution patterns could be avoided by using methyl t-butyl ether as extraction solvent.