Umbilical artery reactivity and ultrastructural changes in pregnancy-induced hypertension and other complicated pregnancies

Vascular contraction of umbilical arteries of pregnant women with preeclampsia

Objective

Potassium channels have an important role in the vascular adaptation during pregnancy and a reduction in the expression of adenosine triphosphate-sensitive potassium channels (Katp) has been linked to preeclampsia. Activation of Katp induces vasodilation; however, no previous study has been conducted to evaluate the effects of the inhibition of these channels in the contractility of preeclamptic arteries. Glibenclamide is an oral antihyperglycemic agent that inhibits Katp and has been widely used in vascular studies.

Methods

To investigate the effects of the inhibition of Katp, umbilical arteries of preeclamptic women and women with healthy pregnancies were assessed by vascular contractility experiments, in the presence or absence of glibenclamide. The umbilical arteries were challenged with cumulative concentrations of potassium chloride (KCl) and serotonin.

Results

There were no differences between the groups concerning the maternal age and gestational age of the patients. The percentage of smokers, caucasians and primiparae per group was also similar. On the other hand, blood pressure parameters were elevated in the preeclamptic group. In addition, the preeclamptic group presented a significantly higher body mass index. The newborns of both groups presented similar APGAR scores and weights.

Conclusion

In the presence of glibenclamide, there was an increase in the KCl-induced contractions only in vessels from the PE group, showing a possible involvement of these channels in the disorder.

Nanoscale imaging of morphological changes of umbilical cord in pre-eclampsia

It is known that pre-eclampsia affects the structure of the umbilical cord including changes in diameter and wall thickness. In this work, the morphological changes of umbilical cords associated with pre-eclampsia were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM images showed the overall structural changes in the umbilical cord, and the AFM imaged the surface of the cord in the nanometer range. The amount of Wharton's jelly was reduced in the cords of pre-eclampsia patients and it was holed along the boundary. Compared to a normal pregnancy, the surface of a pre-eclampsia cord was relatively smooth. In all components (Wharton's jelly, veins, and arteries), the values for surface roughness, Sa (average value of the roughness), Sq (root mean square), and Sz (peak to peak value), were smaller than those of the control (P < 0.05). Especially, the values for Sa of veins were ~fourfold less than those of the controls (P < 0.05). In pre-eclamptic cords, the amount of elastin in veins was increased while that of the artery was decreased.

Regulation of human umbilical artery contractility by different serotonin and histamine receptors

We studied the role of several serotonin (5-HT) and histamine receptors in the regulation of human umbilical artery (HUA) contractility. Among the 5-HT agonists used, only the 5-HT( 2A) and 5HT(1B/D) agonists contracts HUA. The 5-HT-induced contractions were fully inhibited by ketanserin (5-HT(2A) antagonist). The 5-HT( 7)-activation also relaxes and increases intracellular cyclic adenosine monophosphate (cAMP). Among the histamine receptor agonists, only betahistine (H(1) agonist) induced significant contractile effect. Histamine-induced contraction was partially relaxed by pyrilamine (H(1) antagonist). Betahistine-induced contraction was partially blocked by dimaprit (H( 2) agonist) and by the H(3) agonist when a low concentration of forskolin is present. Both, H(2) and H(3) agonists increased the cAMP intracellular levels in HUA smooth muscle. These findings show that in HUA, 5-HT(2A)- and 5-HT(1B/1D)-activation lead to vasoconstriction and 5-HT(7)-activation induces vasorelaxation. Concerning histamine receptors, H(1)-activation induces contraction and H(2)- and H(3)-activation lead to vasorelaxation.

Computerized microscope morphometry of umbilical vessels from pregnancies with intrauterine growth retardation and abnormal umbilical artery Doppler

Computerized microscope morphometry was used to study cross sections from the vessels of the umbilical cord in placentas of patients with intrauterine growth retardation (IUGR) that displayed either normal or abnormal umbilical arteries (UA) Doppler flow velocity waveforms (FVW). Cords from 63 eutrophic fetuses with normal Doppler (controls), 47 IUGR fetuses with normal Doppler and 32 IUGR fetuses with abnormal Doppler underwent morphometric analysis using a highly optimized microscope environment (HOME) and "CordHOME" software. IUGR with an accompanying normal Doppler versus control showed a reduction of Wharton jelly and both the total and lumen vein areas. IUGR with an accompanying pathological Doppler showed a comparable reduction in wall thickness and areas of every vessel. These findings indicate that the hypoplastic umbilical vessels are associated with an increase in placental vascular resistance that may be the consequence of underdevelopment in response to a chronic reduction in placental blood flow.

Reduced contractile effect of endothelin-1 and noradrenalin in human umbilical artery from pregnancies with abnormal umbilical artery flow velocity waveforms

This study on the human umbilical artery was undertaken in order to elucidate possible correlations between changes in response to vasoactive substances in vitro and abnormal umbilical artery flow velocity waveforms in vivo associated with preeclampsia and intrauterine growth retardation. The vascular reactivity to endothelin-1, noradrenalin, serotonin, the thromboxane A2 analogue U46619, substance P and prostacyclin was determined in umbilical artery segments from 13 normal pregnancies and 29 pregnancies complicated with preeclampsia and/or intrauterine growth retardation with normal or abnormal umbilical flow velocity waveforms. The contractile effect in vitro of endothelin-1 and noradrenalin was reduced in segments from pregnancies complicated by abnormal umbilical flow velocity waveforms in vivo. No differences were detected in the contractile effect of serotonin and U46619, or in the relaxatory effect of substance P and prostacyclin. In conclusion, endothelin-1- and noradrenalin-related mechanisms could be involved in the abnormal umbilical flow velocity waveforms associated with preeclampsia and intrauterine growth retardation.

Prostacyclin rather than nitric oxide lowers human umbilical artery tone in vitro

This study was designed to determine vasodilator activities of two endothelium-derived relaxing factors: prostacyclin (PGI2) and nitric oxide (NO) in human umbilical arteries. Isolated vessel segments were contracted by submaximal concentrations of serotonin and bradykinin. These contractions were enhanced after inhibition of prostaglandin formation by the cyclooxygenase inhibitor indomethacin and after removal of the endothelium, both resulting in a pronounced decrease in PGI2 formation. Contractions remained unchanged after treatment of the vessels with nitro-L-arginine, a selective inhibitor of endogenous NO biosynthesis. The efficacy of inhibition of NO biosynthesis was established by a more than 60% reduction in cyclic GMP accumulation. Even inhibition of stimulated NO formation by histamine did not change vascular tone. These data suggest that PGI2 rather than NO is an endothelium-derived relaxing factor in human umbilical arteries.

Term infant asphyxia in Kuwait

In the developing nation of Kuwait, we undertook a case-control study of 43 consecutively born, asphyxiated, term infants. The asphyxia incidence of 9.4/1000 was only slightly higher than that in more developed countries. Severe morbidity occurred in 1.1/1000, and mortality in 1.1/1000. We found significant associations between asphyxia and primiparity, maternal hypertension, consanguinity, increased length of labour, and instrumental deliveries. Maternal age, socio-economic class, maternal illnesses other than diabetes, and breech delivery did not seem to play a role. The fact that the chosen method of delivery failed for a number of the asphyxiated patients, necessitating emergency Caesarian section, suggests that obstetric factors may need closer analysis.