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Conclusion

The crossbred animal mimics symptoms of PIH in blood pressure, 6-ketoPGF,, production, proteinuria and placental and fetal ischemia. Symptoms can be partially prevented by treatment with the platelet-antiaggregating agent ticlopidine.

Urinary tbromboxane IQ an indicator of uterine activity?

W.A. Noort, F.A. de Zwart and M.J.N.C. Keirse, Department of Obstetrics and Gynecology, University Hospital Leiden

There is substantial evidence that prostaglandins play a critical role in the initiation and maintenance of human parturition. Although there are indications that prostanoid synthesis and metabolism change in pregnancy, consistent increases in the levels of prostanoids and their metabolites in plasma, intrauterine tissues or amniotic fluid are only observed during labor. Overall, little attention has been paid to urine as a means of assessing changes in prostanoid production during pregnancy and labor. Most prostanoids are degraded rapidly by the dehydrogenase (PGDH) that is present in the cytoplasm of many celltypes. Thromboxane A, (TXA,) and its stable product TXB,, however, are a poor substrate for PGHD; TXB, excretion could therefore provide a reasonably sensitive measure for any increases in pros- tanoid production that occur in relation to pregnancy and labor. We therefore developed a method for measuring urinary TXB, to investigate how TXB, excretion changes in pregnancy and whether TXB, excretion could provide an appropriate parameter for measuring the increased prostanoid output that is known to be associated with the onset and the progress of labor.

Urine was collected from pregnant women in the first, second and third trimes- ters of pregnancy and during incipient and established labor (n = 12 in each group). Labor was considered as established when strong and regular contractions occurred with a frequency of at least 3 per 10 min together with progressive dilatation; other labors were considered as incipient (in all of these cervical dilatation was less than or equal to 5 cm). Extraction from urine was done with a mixture of ethyl acetate

TABLE VI Urinary TXB, excretion in pregnancy and labor

ng TXBJg creatinine (mean f SEh4) (n = 12)

Non-pregnant Pregnant:

1st trimester 2nd trimester 3rd trimester

In labor: incipient progressive

18k 2

41& 6 51* 1 87i16

105 f 12 183 f 20

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and petroleum ether (60 : 40; v/v) and completed with Seppak C-18 cartridges. The TXB, fraction of each sample was isolated by high-pressure liquid chromatography and measured by radioimmunoassay. To compensate for fluctuations in urinary output results are expressed as a ratio of ng TXB, per g creatinine.

The mean urinary TXB, (rig/g creatinine) levels during all three trimesters of pregnancy are significantly higher than in nonpregnant women (Table VI), with a tendency for urinary TXB, to increase during the course of pregnancy. The urinary TXB, level increased markedly during labor, with levels during established labor being significantly higher than in non-laboring women. Levels in incipient labor, however, showed considerable overlap with those obtained before the onset of labor.

Thus urinary TX$, while not necessarily originating from the pregnant uterus, appears to be an indicator of uterine activity and may reflect an overall increase in prostanoid production during labor.