Magnesium sulfate inhibits the oxytocin-induced production of inositol 1,4,5-trisphosphate in cultured human myometrial cells

William W. Hurd; Viswanathan Natarajan; John R. Fischer; Dawn M. Singh; Shawn G. Gibbs; Victor P. Fomin

doi:10.1067/mob.2002.123897

Magnesium sulfate inhibits the oxytocin-induced production of inositol 1,4,5-trisphosphate in cultured human myometrial cells

William W. Hurd, Viswanathan Natarajan, John R. Fischer, Dawn M. Singh, Shawn G. Gibbs, Victor P. Fomin

Obstetrics, Gynecology and Women's Health

Research output: Contribution to journal › Article › peer-review

15 Scopus citations

Abstract

OBJECTIVE: The purpose of this study was to determine the effects of magnesium sulfate on inositol trisphosphate production and the mechanism of these effects. STUDY DESIGN: Myometrium was obtained at the time of cesarean delivery from women before labor at term. Inositol trisphosphate was measured in the primary myometrial cell cultures after stimulation with oxytocin, sodium fluoride, or Bay K 8644 with or without preincubation with magnesium sulfate or nifedipine. Experiments were performed in either calcium-containing or calcium-free medium that contained egtazic acid and after preincubation with the intracellular calcium chelator BAPTA-acetoxymethylester. Inositol trisphosphate production was measured by radioreceptor assay. In separate experiments, changes in intracellular calcium concentrations ([Ca²⁺]_i) were measured with the use of Fura-2 and spectrophotofluorometry. RESULTS: Oxytocin, sodium fluoride, and Bay K 8644 increased inositol trisphosphate production 2- to 4fold. Preincubation with magnesium sulfate (3 × 10^-3 mol/L) for ≥5 minutes decreased oxytocin-, sodium fluoride-, and Bay K 8644-induced inositol trisphosphate production in either calcium-containing or calcium-free media. Preincubation with BAPTA-acetoxymethylester decreased oxytocin-stimulated inositol trisphosphate production by 78% in calcium-containing media and completely prevented the oxytocin response in calcium-free media. Magnesium sulfate decreased inositol trisphosphate production in calcium-containing media but had no additional effect in calcium-free media. Oxytocin and Bay K 8644 increased [Ca²⁺]ⁱ in either calcium-containing or calcium-free media, and magnesium sulfate reduced this in both cases. CONCLUSION: Magnesium sulfate appears to inhibit phosphatidylinositol-4, 5-bisphosphate-specific phospholipase C activity and subsequent calcium release in cultured myometrial cells by a direct effect on phospholipase C.

Original language	English (US)
Pages (from-to)	419-424
Number of pages	6
Journal	American journal of obstetrics and gynecology
Volume	187
Issue number	2
DOIs	https://doi.org/10.1067/mob.2002.123897
State	Published - Aug 2002

Bibliographical note

Funding Information:
Supported by National Institutes of Health grant HD36692.

Keywords

Calcium
Fura-2
Magnesium sulfate
Myometrium
Phospholipase C
Pregnancy

Access

10.1067/mob.2002.123897

OpenUrl availability

Full text

Cite this

@article{34c25e202801406ab59a2675c19b1e8a,

title = "Magnesium sulfate inhibits the oxytocin-induced production of inositol 1,4,5-trisphosphate in cultured human myometrial cells",

abstract = "OBJECTIVE: The purpose of this study was to determine the effects of magnesium sulfate on inositol trisphosphate production and the mechanism of these effects. STUDY DESIGN: Myometrium was obtained at the time of cesarean delivery from women before labor at term. Inositol trisphosphate was measured in the primary myometrial cell cultures after stimulation with oxytocin, sodium fluoride, or Bay K 8644 with or without preincubation with magnesium sulfate or nifedipine. Experiments were performed in either calcium-containing or calcium-free medium that contained egtazic acid and after preincubation with the intracellular calcium chelator BAPTA-acetoxymethylester. Inositol trisphosphate production was measured by radioreceptor assay. In separate experiments, changes in intracellular calcium concentrations ([Ca2+]i) were measured with the use of Fura-2 and spectrophotofluorometry. RESULTS: Oxytocin, sodium fluoride, and Bay K 8644 increased inositol trisphosphate production 2- to 4fold. Preincubation with magnesium sulfate (3 × 10-3 mol/L) for ≥5 minutes decreased oxytocin-, sodium fluoride-, and Bay K 8644-induced inositol trisphosphate production in either calcium-containing or calcium-free media. Preincubation with BAPTA-acetoxymethylester decreased oxytocin-stimulated inositol trisphosphate production by 78% in calcium-containing media and completely prevented the oxytocin response in calcium-free media. Magnesium sulfate decreased inositol trisphosphate production in calcium-containing media but had no additional effect in calcium-free media. Oxytocin and Bay K 8644 increased [Ca2+]i in either calcium-containing or calcium-free media, and magnesium sulfate reduced this in both cases. CONCLUSION: Magnesium sulfate appears to inhibit phosphatidylinositol-4, 5-bisphosphate-specific phospholipase C activity and subsequent calcium release in cultured myometrial cells by a direct effect on phospholipase C.",

keywords = "Calcium, Fura-2, Magnesium sulfate, Myometrium, Phospholipase C, Pregnancy",

author = "Hurd, {William W.} and Viswanathan Natarajan and Fischer, {John R.} and Singh, {Dawn M.} and Gibbs, {Shawn G.} and Fomin, {Victor P.}",

note = "Funding Information: Supported by National Institutes of Health grant HD36692. ",

year = "2002",

month = aug,

doi = "10.1067/mob.2002.123897",

language = "English (US)",

volume = "187",

pages = "419--424",

journal = "American journal of obstetrics and gynecology",

issn = "0002-9378",

publisher = "Mosby Inc.",

number = "2",

}

TY - JOUR

T1 - Magnesium sulfate inhibits the oxytocin-induced production of inositol 1,4,5-trisphosphate in cultured human myometrial cells

AU - Hurd, William W.

AU - Natarajan, Viswanathan

AU - Fischer, John R.

AU - Singh, Dawn M.

AU - Gibbs, Shawn G.

AU - Fomin, Victor P.

N1 - Funding Information: Supported by National Institutes of Health grant HD36692.

PY - 2002/8

Y1 - 2002/8

N2 - OBJECTIVE: The purpose of this study was to determine the effects of magnesium sulfate on inositol trisphosphate production and the mechanism of these effects. STUDY DESIGN: Myometrium was obtained at the time of cesarean delivery from women before labor at term. Inositol trisphosphate was measured in the primary myometrial cell cultures after stimulation with oxytocin, sodium fluoride, or Bay K 8644 with or without preincubation with magnesium sulfate or nifedipine. Experiments were performed in either calcium-containing or calcium-free medium that contained egtazic acid and after preincubation with the intracellular calcium chelator BAPTA-acetoxymethylester. Inositol trisphosphate production was measured by radioreceptor assay. In separate experiments, changes in intracellular calcium concentrations ([Ca2+]i) were measured with the use of Fura-2 and spectrophotofluorometry. RESULTS: Oxytocin, sodium fluoride, and Bay K 8644 increased inositol trisphosphate production 2- to 4fold. Preincubation with magnesium sulfate (3 × 10-3 mol/L) for ≥5 minutes decreased oxytocin-, sodium fluoride-, and Bay K 8644-induced inositol trisphosphate production in either calcium-containing or calcium-free media. Preincubation with BAPTA-acetoxymethylester decreased oxytocin-stimulated inositol trisphosphate production by 78% in calcium-containing media and completely prevented the oxytocin response in calcium-free media. Magnesium sulfate decreased inositol trisphosphate production in calcium-containing media but had no additional effect in calcium-free media. Oxytocin and Bay K 8644 increased [Ca2+]i in either calcium-containing or calcium-free media, and magnesium sulfate reduced this in both cases. CONCLUSION: Magnesium sulfate appears to inhibit phosphatidylinositol-4, 5-bisphosphate-specific phospholipase C activity and subsequent calcium release in cultured myometrial cells by a direct effect on phospholipase C.

AB - OBJECTIVE: The purpose of this study was to determine the effects of magnesium sulfate on inositol trisphosphate production and the mechanism of these effects. STUDY DESIGN: Myometrium was obtained at the time of cesarean delivery from women before labor at term. Inositol trisphosphate was measured in the primary myometrial cell cultures after stimulation with oxytocin, sodium fluoride, or Bay K 8644 with or without preincubation with magnesium sulfate or nifedipine. Experiments were performed in either calcium-containing or calcium-free medium that contained egtazic acid and after preincubation with the intracellular calcium chelator BAPTA-acetoxymethylester. Inositol trisphosphate production was measured by radioreceptor assay. In separate experiments, changes in intracellular calcium concentrations ([Ca2+]i) were measured with the use of Fura-2 and spectrophotofluorometry. RESULTS: Oxytocin, sodium fluoride, and Bay K 8644 increased inositol trisphosphate production 2- to 4fold. Preincubation with magnesium sulfate (3 × 10-3 mol/L) for ≥5 minutes decreased oxytocin-, sodium fluoride-, and Bay K 8644-induced inositol trisphosphate production in either calcium-containing or calcium-free media. Preincubation with BAPTA-acetoxymethylester decreased oxytocin-stimulated inositol trisphosphate production by 78% in calcium-containing media and completely prevented the oxytocin response in calcium-free media. Magnesium sulfate decreased inositol trisphosphate production in calcium-containing media but had no additional effect in calcium-free media. Oxytocin and Bay K 8644 increased [Ca2+]i in either calcium-containing or calcium-free media, and magnesium sulfate reduced this in both cases. CONCLUSION: Magnesium sulfate appears to inhibit phosphatidylinositol-4, 5-bisphosphate-specific phospholipase C activity and subsequent calcium release in cultured myometrial cells by a direct effect on phospholipase C.

KW - Calcium

KW - Fura-2

KW - Magnesium sulfate

KW - Myometrium

KW - Phospholipase C

KW - Pregnancy

UR - http://www.scopus.com/inward/record.url?scp=0036678360&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0036678360&partnerID=8YFLogxK

U2 - 10.1067/mob.2002.123897

DO - 10.1067/mob.2002.123897

M3 - Article

C2 - 12193936

AN - SCOPUS:0036678360

SN - 0002-9378

VL - 187

SP - 419

EP - 424

JO - American journal of obstetrics and gynecology

JF - American journal of obstetrics and gynecology

IS - 2

ER -

Magnesium sulfate inhibits the oxytocin-induced production of inositol 1,4,5-trisphosphate in cultured human myometrial cells

Abstract

Bibliographical note

Keywords

Access

OpenUrl availability

Other files and links

Fingerprint

Cite this