896

A great deal of evidence suggests that eclampsia andpreeclampsia are states of sympathetic hyperactivity.1, 2

Schobel et al1 measured sympathetic activity in the pero-neal nerve by microneurography and found that thepostganglionic action potential was increased in womenwith preeclampsia. Diffuse cerebral dysfunction (delta

waves) with epileptiform transients (spikes or sharpwaves) was revealed by electroencephalography in pa-tients with eclampsia.3 Preeclampsia and eclampsia areassociated with increased plasma, platelet, and urinarylevels of norepinephrine, a situation that is considered tobe mainly caused by sympathetic nervous system–stimu-lated norepinephrine release.4-7

It is generally accepted that released norepinephrineenhances vascular tone8; however, it was reported thatthe long-lasting vasoconstriction induced by sympatheticnerve stimulation cannot be prevented by complete α-adrenergic receptor blockade,9 which suggests that sym-pathetic nerve–mediated vasoconstriction may also bemediated by factors other than catecholamines. Neuro-peptide Y appears to be an attractive candidate becauseof the noncatecholamine transmitter mediating the vaso-constriction after sympathetic nerve stimulation. Neuro-peptide Y, a 36–amino acid peptide that is mainly foundco-located with norepinephrine in a subset of sympa-

From the Department of Obstetrics and Gynecology, HamamatsuUniversity School of Medicine,a and the Department of Obstetrics andGynecology, Dhaka Medical College and Hospital.bSupported in part by a Grant-in-Aid for Specific Research from theJapanese Ministry of Education and Science (10671529) and aPediatric Research Grant from the Japanese Ministry of Health andWelfare (10-02).Received for publication May 14, 1999; revised August 2, 1999; accepted November 2, 1999.Reprint requests: Naohiro Kanayama, PhD, Department of Obstetricsand Gynecology, Hamamatsu University School of Medicine, 3600Handa-cho, Hamamatsu City 431-3192, Japan.Copyright © 2000 by Mosby, Inc.0002-9378/2000 $12.00 + 0 6/1/104206doi:10.1067/mob.2000.104206

Increased concentrations of plasma neuropeptide Y in patientswith eclampsia and preeclampsia

Selina Khatun, PhD,a Naohiro Kanayama, PhD,a Hossain Md Belayet, PhD,a

Abul Bayes Bhuiyan, MD,b Sultana Jahan, MD,b Anowara Begum, MD,b Takao Kobayashi, PhD,a

and Toshihiko Terao, PhDa

Hamamatsu City, Japan, and Dhaka, Bangladesh

OBJECTIVE: Epinephrine and norepinephrine are associated with the hyperstimulation of the sympatheticnervous system. Neuropeptide Y is a potent vasoconstrictive substance that is released in response to sym-pathetic nerve stimulation.STUDY DESIGN: The concentrations of plasma neuropeptide Y in pregnant patients with eclampsia (n = 8),preeclampsia (n = 8), and normotension (n = 8) were measured by radioimmunoassay on admission and 6days after delivery. Correlations between plasma concentration of neuropeptide Y and mean arterial bloodpressure were also evaluated in these patients on admission and 6 days after delivery.RESULTS: The plasma level of neuropeptide Y in women with eclampsia (P < .001) and preeclampsia (P <.003) was found to be significantly elevated with respect to that in normotensive pregnant women. At 6 daysafter delivery the concentration of plasma neuropeptide Y was significantly decreased in women with eclamp-sia, women with preeclampsia, and women with normotensive pregnancies compared with the value mea-sured on admission (P < .0001, P < .0001, and P < .002, respectively). At admission the plasma neuropep-tide Y level was positively correlated with mean arterial blood pressure in women with eclampsia andpreeclampsia. However, no significant correlations were observed between plasma neuropeptide Y concen-tration and mean arterial blood pressure both at admission and 6 days after delivery in normotensive preg-nant women and 6 days after delivery in women with eclampsia and preeclampsia.CONCLUSION: We have concluded that the level of neuropeptide Y in plasma is increased in women witheclampsia and preeclampsia. Elevated plasma neuropeptide Y levels may play a key role in the developmentof eclampsia and preeclampsia. (Am J Obstet Gynecol 2000;182:896-900.)

Key words: Eclampsia, neuropeptide Y, sympathetic nerve

Obstetrics

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thetic neurons,10, 11 is a potent vasoconstrictor substancethat is released after sympathetic stimulation.12-14

Accordingly, we hypothesized that long-lasting vasocon-striction in the preeclamptic and eclamptic conditions maybe caused by an increase in the plasma level of neuropep-tide Y. This study was therefore designed to investigate theplasma concentrations of neuropeptide Y associated withthe preeclamptic and eclamptic conditions. This is the firstreported investigation of the levels of neuropeptide Y in pa-tients with eclampsia and preeclampsia and their correla-tions with mean arterial blood pressure (MAP).

Material and methods

Subjects. The protocol for this research was approvedby the institutional guidelines for human research. Weinvestigated patients in the third trimester of pregnancyadmitted to Dhaka Medical College Hospital, Bangla-desh, from January 1996 to March 1998 with untreatedeclampsia (n = 8), preeclampsia (n = 8), and normoten-sive pregnancy (n = 8). Nonpregnant healthy volunteerwomen (n = 8) were also enrolled in this study. Properconsent was obtained from each patient or the patient’sguardians (in the case of patients with eclampsia). Thediagnosis of eclampsia was made if a woman had ≥1episode of tonoclonic seizure in the presence of other ev-idence of preeclampsia and the absence of either a his-tory of a seizure disorder or evidence for another cause,such as trauma or infection.15 Preeclampsia was diag-nosed on the basis of a blood pressure ≥140/90 mm Hgon two occasions ≥6 hours apart or a rise of >30 mm Hgsystolic or >15 mm Hg diastolic above baseline bloodpressure with proteinuria of ≥300 mg/24 h. None of thewomen had hypertension before 20 weeks’ gestation.16

All cases complicated by essential hypertension, cardio-vascular disease, diabetes, chronic renal disease, plateletdisorders, maternal or fetal infection, autoimmune disor-ders, and epilepsy were excluded from this study. All nor-motensive pregnant patients were entirely healthythroughout the pregnancy and were admitted for deliv-ery. The subjects were comparable with each other withrespect to age, body weight, and duration of gestation.

The important clinical characteristics of the patients aresummarized in Table I.

Sample collection. Blood and midstream urine sampleswere collected in the morning in all cases except those ofthe patients with eclampsia, among whom collectionswere performed during admission through the emer-gency department of the hospital. None of the patientswith eclampsia had received any antihypertensive or anti-convulsive drugs before collection of blood. Peripheralvenous blood samples were collected from the antecu-bital vein with a 19-gauge needle immediately after themeasurement of blood pressure according to the firstand fifth Korotkoff sounds with the patient in the recum-bent position. Blood was drawn into tubes containingsodium ethylenediaminetetraacetic acid and aprotininon admission and 6 days after delivery for the measure-ment of neuropeptide Y. Samples were centrifuged at2000g for 20 minutes, divided into aliquots under sterileconditions, and stored at –80°C. Samples obtained inBangladesh were transported by air on dry ice at –40°Cwithin 16 hours to Hamamatsu University School ofMedicine, Hamamatsu City, Japan. There were no signifi-cant differences among the subject groups in time ofstorage or time from venipuncture to centrifugation.

Analytic methods. Plasma neuropeptide Y concentra-tion was measured with a radioimmunoassay kit (Penin-sula Laboratories Inc, San Carlos, Calif) with antiserumas described previously.17 A semiquantitative assay for uri-nary protein was performed with Urolab sticks (SankyoCo, Ltd, Tokyo, Japan). Urinary protein was classified asfollows: mild, 1+; moderate, 2+; severe, 3+.

Statistical analysis. Results are expressed as mean ± SD.Analysis of variance for factorial measure followed byBonferroni-Dunn test was used for multiple comparison.P < .05 was considered significant for all comparisons.Regression line and correlation coefficients were also cal-culated. P values were obtained with Fisher r to z analysis.

Results

Plasma neuropeptide Y concentrations in patients witheclampsia, patients with preeclampsia, normotensive

Table I. Characteristics of pregnant women with eclampsia, pregnant women with preeclampsia, normotensive preg-nant women, and normotensive nonpregnant women

Normotensive Normotensive Eclampsia (n = 8) Preeclampsia (n = 8) pregnant (n = 8) nonpregnant (n = 8)

Age (y, mean ± SD) 23.6 ± 3.50 23.0 ± 2.90 0022.6 ± 3.70 024.0 ± 2.8Body weight (kg, mean ± SD) 71.5 ± 6.30 69.6 ± 4.30 065.2 ± 4.7 050.7 ± 3.3Parity Primiparous Primiparous Primiparous —Gestational age (wk, mean ± SD) 35.2 ± 2.90 36.8 ± 3.10 038.2 ± 3.3 —Systolic blood pressure (mm Hg, mean ± SD) 168.6 ± 16.7* 160.9 ± 16.3* 118.9 ± 7.2 110.4 ± 6.6Diastolic blood pressure (mm Hg, mean ± SD) 114.8 ± 9.3*0 105.6 ± 11.2* 078.4 ± 5.5 074.1 ± 6.2Proteinuria (paper stick method) Moderate to severe Mild to moderate Nil Nil

*P < .05, compared with normotensive pregnant patients (factorial analysis of variance).

898 Khatun et al April 2000Am J Obstet Gynecol

pregnant women, and normotensive nonpregnantwomen are shown in Fig 1. Plasma neuropeptide Y con-centrations were 4- and 2-fold higher in patients witheclampsia and preeclampsia, respectively, than in nor-motensive pregnant women (P < .001 and P < .003, respectively). Moreover, the plasma neuropeptide Y concentration in normotensive pregnant women was also significantly higher than in nonpregnant volunteers(P < .02).

The concentrations of plasma neuropeptide Y in pa-tients with eclampsia, patients with preeclampsia, andnormotensive pregnant women on admission and 6 daysafter delivery are shown in Fig 2. The plasma neuropep-tide Y concentrations 6 days after delivery in patients witheclampsia and preeclampsia were significantly decreasedwith respect to values at admission (P < .0001). The con-centration of neuropeptide Y in normotensive pregnantwomen 6 days after delivery was also significantly de-creased with respect to that at admission (P < .002).

The correlations between plasma neuropeptide Y con-centrations and MAP on admission in patients witheclampsia (after eclamptic seizure), patients withpreeclampsia, and normotensive pregnant patients areshown in Fig 3. MAP was positively correlated with plasmaneuropeptide Y concentration in patients with eclampsia(r = 0.791; P < .0002) and preeclampsia (r = 0.809; P <.0003). No significant correlation was found betweenplasma neuropeptide Y concentration and MAP on ad-mission among normotensive pregnant women, nor werethere any significant correlations found between plasmaneuropeptide Y concentration and MAP among patientswith eclampsia, patients with preeclampsia, and nor-motensive pregnant women 6 days after delivery (Fig 4).

Comment

Plasma neuropeptide Y concentrations were higher inpatients with eclampsia and preeclampsia than in nor-motensive pregnant women. It was also found thatplasma neuropeptide Y concentration had returned al-most to reference values of normotensive nonpregnantwomen 6 days after delivery. Plasma neuropeptide Y con-centration was also increased significantly in normoten-sive pregnant women with respect to that in nonpregnantvolunteer women. Plasma neuropeptide Y concentra-tions were influenced by the acute stress situation thatmarked the response of the sympathetic nervous system.

Eclampsia and preeclampsia are pathologic conditionsof unknown etiology, and a large number of hypotheseshave been put forward to explain their underlying mech-anisms. However, it is well known that the predominantoccurrence is during late pregnancy, mainly in primi-gravid women. Among the provocative factors suggested,the role of the sympathetic nervous system is important.Greater concentrations of plasma norepinephrine andepinephrine and increased sensitivity to infused norepi-nephrine in women with preeclampsia than in normoten-sive pregnant women were also demonstrated.5, 18, 19

Recently, we reported that localized cold stress inducedsympathetic stimulation that resulted in hypercate-cholaminemia, which was responsible for vasospasms ofvessels.20 The continuous increase in vessel tone could in-duce hypertension. Moreover, we demonstrated that in-tense staining of neuropeptide Y in the adrenal medullain the cold-stressed rats implied increased release of neu-ropeptide Y during sympathetic stimulation. It is knownthat neuropeptide Y can increase the biosynthesis of cate-

Fig 1. Plasma neuropeptide Y (NPY) concentrations in patientswith eclampsia, patients with preeclampsia, normotensive preg-nant women, and normotensive nonpregnant women. Plasmaneuropeptide Y concentrations in patients with eclampsia andpreeclampsia were markedly increased with respect to those innormotensive pregnant women. Horizontal rules, Mean ± SD; n =8. Asterisk, P < .05, versus normotensive pregnant women.

Fig 2. Plasma neuropeptide Y (NPY) concentrations in patientswith eclampsia, patients with preeclampsia, and normotensivepregnant women. Plasma neuropeptide Y concentrations in pa-tients with eclampsia, patients with preeclampsia, and nor-motensive pregnant women were markedly greater on admis-sion (black bars) than 6 days after delivery (gray bars). Bar heights,Mean; error bars, SD; n = 8. Asterisk, P < .05, versus 6 days after de-livery.

Volume 182, Number 4 Khatun et al 899Am J Obstet Gynecol

cholamines.21 Stress-induced increases in norepineph-rine and epinephrine concentrations are responsible forrepeated transient vasospasms,22 and both neuropeptideY and catecholamines are essential to sustain vasocon-striction.23 Previous observation suggests that the neu-ropeptide Y concentration in plasma is increased withgestational age and is significantly increased during par-turition24 and that neuropeptide Y concentrations in themyometrium are increased in pregnancies complicatedby preeclampsia.25 Our results are compatible with previ-ous observations of stress-induced release of neuropep-tide Y along with catecholamines from sympathetic nerveendings.26

We found that the neuropeptide Y concentrations inpatients with eclampsia and preeclampsia were signifi-cantly correlated with MAP on admission. The markedincrease in plasma neuropeptide Y concentration in theeclamptic and preeclamptic conditions might induceand sustain strong vasoconstriction, resulting in hyper-tension. We also observed that 6 days after delivery theplasma neuropeptide Y concentrations and MAP had re-turned to levels equivalent to those of normotensive non-pregnant women. As a result no correlation was foundbetween MAP and plasma neuropeptide Y concentra-tions 6 days after delivery. Petraglia et al27 detected im-munoreactive neuropeptide Y in human placenta and re-ported that neuropeptide Y plasma concentrations didnot increase during normal pregnancy. There is a possi-bility that the source of plasma neuropeptide Y in pa-tients with preeclampsia and eclampsia is not only sympa-thetic nerve endings but also placenta. A sharp decreasein plasma neuropeptide Y concentrations after deliveryin those patients may be a result of expulsion of a pla-

centa containing neuropeptide Y. It is also important tonote that plasma neuropeptide Y concentration was alsoincreased during parturition in normotensive nonpreg-nant women but that no positive correlation was ob-served between MAP and neuropeptide Y concentration.The pathophysiologic importance of a positive correla-tion between plasma neuropeptide Y level and MAP indi-cates that increased concentrations on admission ofplasma neuropeptide Y in patients with eclampsia andpreeclampsia were responsible for the development ofclinical features of eclampsia and preeclampsia. Suchcorrelations found in the eclamptic and preeclampticconditions may have been a result of long-lasting va-sospasms caused by hyperactivity of the sympathetic ner-vous system.

This study showed that plasma neuropeptide Y concen-trations in patients with eclampsia and preeclampsiawere significantly increased with respect to those in nor-motensive pregnant women. Increased plasma neu-ropeptide Y concentrations may play a key role in the development of clinical features of eclampsia and pre-eclampsia.

We thank Drs Faruque A. Azim, and A.J.E. NaharRahman, Department of Pathology, Dhaka MedicalCollege and Hospital, Bangladesh, and Dr A.K. AzadKhan, Bangladesh, for useful discussion and Mr NaniGopal Banik, Bangladesh, for invaluable help and experttechnical assistance.

REFERENCES

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Fig 4. Correlation between plasma neuropeptide Y (NPY) con-centrations and MAP 6 days after delivery in patients witheclampsia (filled diamonds; r = 0.067; P not significant), patientswith preeclampsia (open diamonds with middle rule; r = 0.092; P notsignificant), and normotensive pregnant women (open triangles; r= –0.039; P not significant). Plasma neuropeptide Y concentra-tions were not significantly correlated with MAP 6 days after de-livery in any group.

Fig 3. Correlations between plasma neuropeptide Y (NPY) con-centrations and MAP on admission in patients with eclampsia(filled diamonds; r = 0.791; P < .0002), patients with preeclampsia(open diamonds with middle rule; r = 0.809; P < .0003), and nor-motensive pregnant women (open triangles; r = 0.080; P not signif-icant). Plasma neuropeptide Y concentration was positively cor-related with MAP in patients with eclampsia and preeclampsia(regression lines). P values were obtained with Fisher r to z analysis.

900 Khatun et al April 2000Am J Obstet Gynecol

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