PLASMA ENDOTHELIN, ATRIAL-NATRIURETIC-PEPTIDE (ANP) AND UTERINE AND UMBILICAL ARTERY FLOW VELOCITY WAVE-FORMS IN HYPERTENSIVE PREGNANCIES

Objective To investigate the relation between concentrations of endothelin and atrial natriuretic peptide (ANP) in maternal plasma and vasospasm in the uterine and umbilical arteries as detected by duplex pulsed colour Doppler ultrasonography in hypertensive pregnancies. Design An observational study. Subjects 32 women admitted consecutively to hospital with pregnancy induced hypertension (seven without proteinuria and 25 with proteinuria) and 78 healthy pregnant women examined at 28-40 weeks gestation. Main outcome measures Systolic/diastolic (S/D) ratio in flow velocity waveforms (FVWs) and plasma concentrations of endothelin and ANP in the 32 women with pregnancy induced hypertension; plasma concentrations of endothelin and ANP in 78 healthy pregnant women (controls). Results Pathological FVWs suggesting vasospasm in the uterine, or umbilical artery, or both arteries, were found in 12 women with hypertension. Plasma ANP was significantly higher (P = 0.03) in the women with hypertension and pathological FVWs (median 23.0, range 10.1-52.8 pmol/l) than in those with hypertension and normal FVWs, (median 13.8, range 5.3-42.3 pmol/l) but corresponding plasma endothelin levels did not show any significant difference (median 1.63, range 0.51-3.33 pmol/l and median 1.38, range 0.51-3.51 pmol/l, respectively). Conclusion Local release of endothelin from the vascular endothelium is thought to cause vasospasm in pregnancy induced hypertension but this does not seem to increase the concentration of endothelin in the maternal peripheral plasma, probably because of its rapid disappearance from the blood circulation. As ANP dilates the blood vessels, the increase of its release in hypertensive pregnancies may be a compensatory mechanism against vasospasm.