Obstetrics & Gynecology Track the topics, authors and articles important to you
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Obstetrics & Gynecology 2001;97:893-897
© 2001 by The American College of Obstetricians and Gynecologists
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by HALHALI, A.
Right arrow Articles by LARREA, F.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by HALHALI, A.
Right arrow Articles by LARREA, F.

ORIGINAL RESEARCH

Calcitonin Gene- and Parathyroid Hormone-Related Peptides in Preeclampsia: Effects of Magnesium Sulfate

ALI HALHALI, PhD, SUNIL J. WIMALAWANSA, PhD, VERONICA BERENTSEN, BSc, EUCLIDES AVILA, MSc, CHANDRA SEKHAR THOTA, PhD and FERNANDO LARREA, MD

From the Department of Reproductive Biology, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, México D.F., México; and the Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas.

Address reprint requests to: Ali Halhali, PhD Department of Reproductive Biology Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán Vasco de Quiroga No 15 Col. Tlalpan CP 14000, México, DF México E-mail: alih{at}quetzal.innsz.mx


   Abstract
Top
Abstract
Materials and Methods
 Results
 Discussion
 References
 
Objective: To determine whether circulating levels of calcitonin gene-related peptide (CGRP) and parathyroid hormone-related peptide (PTHrP) are altered in preeclampsia, and to assess the effects of magnesium sulfate therapy on circulating levels of these two peptides.

Methods: The study population included 25 women with preeclampsia and 25 normotensive controls of similar gestational age. The effects of magnesium sulfate therapy were evaluated in 17 of the 25 preeclamptic women. Circulating levels of immunoreactive CGRP and PTHrP, including calcium, magnesium, and phosphate in the maternal and umbilical cord serum were measured.

Results: The frequency of preeclampsia subjects with nondetectable PTHrP (under 3 pg/mL) was significantly higher (92% versus 48%, P < .001), whereas maternal serum CGRP levels were significantly lower (50 ± 19 versus 90 ± 23 pg/mL, P < .001). Similarly, the frequency of newborns with nondetectable PTHrP levels in umbilical serum was significantly higher (68% versus 36%, P < .05), whereas the levels of CGRP were significantly lower (67 ± 17 versus 79 ± 16 pg/mL, P < .05). Magnesium sulfate treatment resulted in a significant increase in maternal circulating CGRP levels (64 ± 17 versus 47 ± 18 pg/mL, P < .05) with no changes in PTHrP.

Conclusion: Maternal circulating PTHrP and CGRP concentrations were significantly lower in women with preeclampsia, which may contribute to the development and maintenance of hypertension during pregnancy. Furthermore, magnesium sulfate therapy increased the levels of CGRP in the maternal circulation.

Among the several alterations observed in preeclampsia, those in calcium metabolism such as low urinary calcium excretion and circulating 1,25-dihydroxyvitamin D levels have been well documented.1,2 Among the components of the vasodilator system, both calcitonin gene-related peptide (CGRP) and parathyroid hormone-related peptide (PTHrP) may be considered as important calcium-related regulators of blood pressure.3–5 Whether calcium supplementation during pregnancy decreases the incidence of preeclampsia is controversial.6,7 However, we demonstrated previously a significant reduction of blood pressure and increased plasma CGRP after oral calcium supplementation in humans,3 suggesting a beneficial effect of this mineral on blood pressure, which might in part be mediated by CGRP.4

PTHrP, another potent vasodilator,8 is responsible for humoral hypercalcemia of malignancy5 and the fetoplacental unit is considered as a nontumor site of PTHrP production.5 As circulating levels of PTHrP increase also during pregnancy,9 it has been suggested that both CGRP and PTHrP may play a role in blood pressure regulation under this physiologic condition. In this study, we examined whether the concentrations of these two vasodilator peptides are altered in preeclampsia. In addition, the effects of magnesium sulfate therapy on circulating CGRP and PTHrP levels were also evaluated.


   Materials and Methods
Top
Abstract
 Materials and Methods
Results
 Discussion
 References
 
Maternal and umbilical cord blood samples were collected at delivery in accordance with the guidelines of the Declaration of Helsinki. This study protocol was approved by the Human Ethics Committee of the Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, and each woman signed a written informed consent form. This cross-sectional study was done at delivery and included 25 preeclamptic and 25 normotensive pregnant women and their respective newborns. This number of subjects was calculated to have more than 90% statistical sample power at a confidence level of 95%. For each experimental case, an eligible control subject was chosen in a consecutive manner. All the subjects had similar demographic backgrounds. They were mestizoes and belonged to a low socioeconomic urban population of Mexico City. Calcium intake was not determined in the present study, however, we found previously that calcium content in a standard Mexican diet is about 900 mg/day.10

The diagnosis of preeclampsia was based on the simultaneous presence of hypertension (systolic blood pressure at least 140 mmHg or diastolic blood pressure at least 90 mmHg), and proteinuria (at least 2+ protein on dipstick).11 All 25 preeclamptic women received magnesium sulfate therapy, but paired blood samples were obtained only from 17 women before and after treatment. The remaining eight preeclamptic women were not studied after treatment because they were temporarily not available; however, all preeclamptic women had similar clinical characteristics and disease course. Magnesium sulfate treatment consisted of a loading dose of 4 g administered intravenously over a period of 30 minutes followed by a maintenance dose of 1 g per hour for 6 hours.12 Patients with known preexisting hypertension or previous preeclampsia, including liver, renal, heart, or any other endocrine disorders, as well as the use of nutritional supplements (calcium, vitamin D), diuretics, or any kind of hormonal treatment, were not included in this study. Only women delivering a single newborn with Apgar scores of 7–10 were included. Maternal and umbilical cord blood were obtained and serum samples aliquoted and frozen at - 70C until assayed.

Serum ionized calcium and magnesium were measured by ion-selective electrodes using a Nova 8 CRT electrolyte analyzer (Nova Biomedical, Waltham, MA). Serum total calcium and magnesium were measured by atomic absorption spectrophotometry (Perkin Elmer 2380, Norwalk, CT), and inorganic phosphorus concentrations were assessed as described previously.13 For PTHrP measurements, blood samples were collected in tubes containing protease inhibitors, aprotinin (500 Kallikrein units per liter) and leupeptin (2.5 mg/L), as previously reported.14 Serum immunoreactive PTHrP concentrations were measured by a commercial immunoradiometric assay kit (Diagnostic Systems Laboratories, Webster, TX). The sensitivity was 3 pg/mL, and intra- and interassay coefficients of variation were 8.9% and 10%, respectively. Serum immunoreactive CGRP was assayed using a commercial radioimmunoassay kit (Phoenix Pharmaceuticals, Inc., Mountain View, CA). The sensitivity was 7 pg/mL, and the intra- and inter-assay coefficients of variation were less than 4.5% and 7.5%, respectively.

Results are presented as mean ± standard deviation (SD). Statistical differences between the two groups were analyzed by Mann–Whitney U test. Comparison of frequencies was done using chi-square. Variables before and after magnesium sulfate treatment in the preeclamptic group was analyzed by Wilcoxon signed rank test. Differences were considered statistically significant at P < .05.


   Results
Top
Abstract
 Materials and Methods
 Results
Discussion
 References
 
Table 1Go summarizes the clinical characteristics of mothers and their newborns. Maternal and gestational ages and frequency of parity were similar between groups. For preeclamptic women, newborn birth weight was significantly lower, whereas the frequency of cesarean delivery was higher than in controls.


View this table:
[in this window]
[in a new window]
  		Table 1. Clinical Characteristics
 
Table 2Go summarizes maternal serum levels of minerals, PTHrP, and CGRP in the two groups. With preeclampsia, circulating levels of total and ionized calcium were significantly lower, whereas the frequency of subjects with nondetectable serum PTHrP (under 3 pg/mL) was significantly higher than in controls. No differences were observed in maternal circulating levels of total and ionic magnesium, and inorganic phosphorus between the groups. As shown in Table 2Go, maternal serum CGRP levels were significantly lower in preeclamptic women.


View this table:
[in this window]
[in a new window]
  		Table 2. Maternal Serum Concentrations of Minerals, PTHrP, and CGRP
 
The effects of magnesium sulfate treatment on circulating levels of minerals, PTHrP, and CGRP were evaluated in preeclamptic women (Table 3Go). This treatment was followed by increased maternal serum total and ionic magnesium, whereas a decrease in total and ionized calcium levels was observed. There were no significant changes in maternal serum inorganic phosphorus and PTHrP levels. Maternal serum CGRP concentrations increased significantly after magnesium sulfate treatment. In addition, circulating levels of this peptide were significantly higher in the umbilical serum than in maternal serum before magnesium sulfate treatment (67 ± 19 versus 50 ± 19 pg/mL, P < .05) (Tables 2Go and 4Go). In contrast, circulating levels of CGRP were similar in the umbilical and maternal serum of controls (Tables 2Go and 4Go). As can be seen in Table 4Go, umbilical serum levels of total calcium, ionic calcium, and CGRP were significantly lower, and total and ionic magnesium as well as the number of subjects with low PTHrP were significantly higher with preeclampsia. No differences were found in umbilical cord serum levels of inorganic phosphorus.


View this table:
[in this window]
[in a new window]
  		Table 3. Maternal Serum Concentrations of Minerals, PTHrP, and CGRP Before and After Magnesium Sulfate
 

View this table:
[in this window]
[in a new window]
  		Table 4. Umbilical Serum Concentrations of Minerals, PTHrP, and CGRP
 

   Discussion
Top
Abstract
 Materials and Methods
 Results
 Discussion
References
 
The present study demonstrated that in preeclampsia maternal and umbilical cord serum PTHrP and CGRP levels were lower than in normotensive pregnant women. This observation may indicate that these peptides may be involved, at least in part, in the development of hypertension and reduced newborn birth weight in preeclampsia.2,11,15 This suggestion is not unlikely, because alterations of both PTHrP and CGRP, potent vasodilators that are widely distributed in the body, are associated with decreased blood flow in the human uteroplacental unit.8,16,17 In support of this concept, the use of PTHrP antagonists in an in vitro human placental perfusion model17 suggests the participation of these peptides as regulators of endothelial vascular responses occurring normally during pregnancy.

Preeclampsia is associated with several alterations such as in calcium metabolism, blood pressure, and intrauterine blood flow.1,2,11,15 Indeed, in this study, maternal calcium concentrations were lower with preeclampsia, in agreement with previous reports from this and other laboratories.1,2 In addition, we also found lower maternal PTHrP and CGRP concentrations in preeclamptics, suggesting that hypertension in preeclampsia may be associated, at least in part, with alterations in the circulating levels of these two peptides. In support of this concept, CGRP has been considered as a mediator of calcium effects on blood pressure.3,4 Furthermore, administration of CGRP in experimental preeclamptic and nonpreeclamptic rats inhibited the hypertensive effects of NG-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthesis.18–23

In the case of preeclamptic women, the role of CGRP remains unknown.24,25 In one study,24 the absence of differences in serum CGRP levels between preeclamptic and normotensive women was probably a result of the wide range of values found in both groups. In another study,25 the authors failed to observe a difference in circulating levels of CGRP between nonpregnant and pregnant women despite the well-known increase of this peptide in maternal serum during pregnancy.26,27 In contrast, our results and those of Zhang et al28 showing significantly lower CGRP circulating levels in preeclampsia and pregnancy-induced hypertension, respectively, indicate that CGRP might also be considered as an additional regulating factor of blood pressure. Because PTHrP increases bone resorption and phosphate urinary excretion,9 low circulating levels of this peptide in the preeclamptic group did not result in significant changes in maternal serum inorganic phosphorus concentrations. A longitudinal study to support the relationship between preeclampsia and both PTHrP and CGRP to establish potential indicators for the development, prevention, and treatment of the disease would be valuable.

In the present study we investigated the effects of magnesium sulfate on serum calcium, PTHrP and CGRP levels. As previously described,12,29,30 magnesium sulfate treatment resulted in a significant decrease in total and ionized calcium. In addition, treatment was followed by a significant increase in maternal serum levels of CGRP, but not in PTHrP. Umbilical cord serum CGRP levels, although similar to those in maternal blood, were significantly higher than those observed in the maternal circulation before treatment. This observation suggests that fetal CGRP synthesis could be also affected by magnesium sulfate. Inasmuch as maternal and umbilical circulating levels of CGRP were similar in the normotensive group, which support an effect of magnesium sulfate upon maternal and fetal CGRP synthesis, the mechanism involved in this effect deserves to be further investigated.


   Footnotes
 
This work was supported in part by grants from the National Council of Science and Technology (CONACYT, México, 26238-M), the Special Programme of Research, Development and Research Training in Human Reproduction of the World Health Organization (Geneva, Switzerland) and Texas Higher Education Coordinating Board grant 004-59-005 (Texas, USA).

We thank the Hospital General M. Gea Gonzalez, México D.F., for blood sample donations.

PII S0029-7844(01)01351-5

Received September 28, 2000. Received in revised form December 29, 2000. Accepted February 8, 2001.


   References
Top
Abstract
 Materials and Methods
 Results
 Discussion
 References
 
1. Seely EW, Wood RJ, Brown EM, Graves SW. Lower serum ionized calcium and abnormal calciotropic hormone levels in preeclampsia. J Clin Endocrinol Metab 1992;74:1436–40.[Abstract]

2. Halhali A, Tovar AR, Torres N, Bourges H, Garabédian M, Larrea F. Preeclampsia is associated with low circulating levels of insulin-like growth factor I and 1,25-dihydroxyvitamin D in maternal and umbilical cord compartments. J Clin Endocrinol Metab 2000;85: 1828–33.[Abstract/Free Full Text]

3. Wimalawansa SJ. Antihypertensive effects of oral calcium supplementation is mediated through the potent vasodilator CGRP. Am J Hypertens 1993;6:996–1002.[Medline]

4. Wimalawansa SJ, Supowit SC, DiPette DJ. Mechanisms of the antihypertensive effects of dietary calcium and role of calcitonin gene-related peptide in hypertension. Can J Physiol Pharmacol 1995;73:981–5.[Medline]

5. Wysolmerski JJ, Stewart AF. The physiology of parathyroid hormone-related protein: An emerging role as a developmental factor. Annu Rev Physiol 1998;60:431–60.[Medline]

6. Levine RJ, Hauth JC, Curet LB, Sibai BM, Catalano PM, Morris CD, et al. Trial of calcium to prevent preeclampsia. N Engl J Med 1997;337:69–76.[Abstract/Free Full Text]

7. Lopez-Jaramillo P. Calcium, nitric oxide, and preeclampsia. Semin Perinatol 2000;24:33–6.[Medline]

8. Mandsager NT, Brewer AS, Myatt L. Vasodilator effects of parathyroid hormone, parathyroid hormone-related protein, and calcitonin gene-related peptide in the human fetal-placental circulation. J Soc Gynecol Invest 1994;1:19–24.[Medline]

9. Kovacs CS, Kronenberg HM. Maternal-fetal calcium and bone metabolism during pregnancy, puerperium, and lactation. Endocr Rev 1997;18:832–72.[Abstract/Free Full Text]

10. Halhali A, Bourges H, Carrillo A, Garabédian M. Lower circulating insulin-like growth factor I and 1,25-dihydroxyvitamin D levels in preeclampsia. Rev Invest Clin 1995;47:259–66.[Medline]

11. National High Blood Pressure Education Program Working Group. National High Blood Pressure Education Program Working Group on high blood pressure in pregnancy. Am J Obstet Gynecol 1990;163:1689–712.

12. Cruikshank DP, Pitkin RM, Reynolds WA, Williams GA, Hargis GK. Effects of magnesium sulfate treatment on perinatal calcium metabolism. I. Maternal and fetal responses. Am J Obstet Gynecol 1979;134:243–9.[Medline]

13. Fiske CH, SubbaRow Y. The colorimetric determination of phosphorus. J Biol Chem 1925;66:375–400.[Free Full Text]

14. Pandian MR, Morgan CH, Carlton E, Segre GV. Modified immunoradiometric assay of parathyroid hormone-related protein: Clinical application in the differential diagnosis of hypercalcemia. Clin Chem 1992;38:282–8.[Abstract/Free Full Text]

15. Redman CWG. Current topic: Pre-eclampsia and the placenta. Placenta 1991;12:301–8.[Medline]

16. Graf AH, Hutter W, Hacker GW, Steiner H, Anderson V, Staudach A, et al. Localization and distribution of vasoactive neuropeptides in the human placenta. Placenta 1996;17:413–21.[Medline]

17. Macgill K, Moseley JM, Martin TJ, Brennecke SP, Rice GE, Wlodek ME. Vascular effects of PTHrP (1–34) and PTH (1–34) in the human fetal-placental circulation. Placenta 1997;18:587–92.[Medline]

18. Yallampalli C, Dong YL, Wimalawansa SJ. Calcitonin gene-related peptide reverses the hypertension and significantly decreases the fetal mortality in pre-eclampsia rats induced by NG-nitro-L-arginine methyl ester. Hum Reprod 1996;11:895–9.[Abstract/Free Full Text]

19. Gangula PR, Supowit SC, Wimalawansa SJ, Zhao H, Hallman DM, DiPette DJ, et al. Calcitonin gene-related peptide is a depressor in NG-nitro-L-arginine methyl ester-induced hypertension during pregnancy. Hypertension 1997;29:248–53.[Abstract/Free Full Text]

20. Gangula PR, Wimalawansa SJ, Yallampalli C. Progesterone up-regulates vasodilator effects of calcitonin gene-related peptide in NG-nitro-L-arginine methyl ester-induced hypertension. Am J Obstet Gynecol 1997;176:894–900.[Medline]

21. Wimalawansa SJ, Yallampalli C. Pre-eclamptic toxemia: Potential new therapy based on animal studies. Ceylon Med J 1998;43:138–46.[Medline]

22. Gangula PR, Zhao H, Supowit S, Wimalawansa S, DiPette D, Yallampalli C. Pregnancy and steroid hormones enhance the vasodilatation responses to CGRP in rats. Am J Physiol 1999;276: H284–8.

23. Grewal M, Cuevas J, Chaudhuri G, Nathan L. Effects of calcitonin gene-related peptide on vascular resistance in rats: Role of sex steroids. Am J Physiol 1999;276:H2063–8.

24. Kraayenbrink AA, Dekker GA, van Kamp GJ, van Geijn HP. Endothelial vasoactive mediators in preeclampsia. Am J Obstet Gynecol 1993;169:160–5.[Medline]

25. Schiff E, Friedman SA, Sibai BM, Kao L, Schifter S. Plasma and placental calcitonin gene-related peptide in pregnancies complicated by severe preeclampsia. Am J Obstet Gynecol 1995;173: 1405–9.[Medline]

26. Stevenson JC, MacDonald DWR, Warren RC, Booker MW, Whitehead MJ. Increased concentration of circulating CGRP during normal human pregnancy. Br Med J 1986;293:1329–30.

27. Saggese G, Bertelloni S, Baroncelli GI, Pelletti A, Benedetti U. Evaluation of a peptide family encoded by the calcitonin gene in selected healthy pregnant women. A longitudinal study. Horm Res 1990;34:240–4.[Medline]

28. Zhang W, Zhao Y, Wang L. The changes of plasma calcitonin gene-related peptide level in women with normal pregnancy and pregnancy induced hypertension. Chung Hua Fu Chan Ko Tsa Chih 1998;33:715–6.

29. Cruikshank DP, Pitkin RM, Donnelly E, Reynolds WA. Urinary magnesium, calcium, and phosphate excretion during magnesium sulfate infusion. Obstet Gynecol 1981;58:430–4.[Abstract/Free Full Text]

30. Cruikshank DP, Chan GM, Doerrfeld D. Alterations in vitamin D and calcium metabolism with magnesium sulfate treatment of preeclampsia. Am J Obstet Gynecol 1993;168:1170–6.[Medline]




This article has been cited by other articles:


Home page
 Biol. Reprod.Home page
Y.-L. Dong, D. M. Reddy, K. E. Green, M. S. Chauhan, H.-Q. Wang, M. Nagamani, G. D.V. Hankins, and C. Yallampalli
Calcitonin Gene-Related Peptide (CALCA) Is a Proangiogenic Growth Factor in the Human Placental Development
Biol Reprod, May 1, 2007; 76(5): 892 - 899.
[Abstract] [Full Text] [PDF]

Home page
 Mol Hum ReprodHome page
K.E. Green, C. Thota, G.D.V. Hankins, C. Yallampalli, and Y.-L. Dong
Calcitonin gene-related peptide stimulates human villous trophoblast cell differentiation in vitro
Mol. Hum. Reprod., July 1, 2006; 12(7): 443 - 450.
[Abstract] [Full Text] [PDF]

Home page
 J. Clin. Endocrinol. Metab.Home page
Y.-L. Dong, K. E. Green, S. Vegiragu, G. D. V. Hankins, E. Martin, M. Chauhan, C. Thota, and C. Yallampalli
Evidence for Decreased Calcitonin Gene-Related Peptide (CGRP) Receptors and Compromised Responsiveness to CGRP of Fetoplacental Vessels in Preeclamptic Pregnancies
J. Clin. Endocrinol. Metab., April 1, 2005; 90(4): 2336 - 2343.
[Abstract] [Full Text] [PDF]

Home page
 Biol. Reprod.Home page
E. Maioli, V. Fortino, and A. Pacini
Parathyroid Hormone-Related Protein in Preeclampsia: A Linkage Between Maternal and Fetal Failures
Biol Reprod, December 1, 2004; 71(6): 1779 - 1784.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by HALHALI, A.
Right arrow Articles by LARREA, F.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by HALHALI, A.
Right arrow Articles by LARREA, F.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS