Gestational and Hormonal Effects on Magnesium Sulfate’s Ability to Inhibit Mouse Uterine Contractility

May 21, 2020Reproductive sciences (Thousand Oaks, Calif.)

How Pregnancy Stage and Hormones Affect Magnesium Sulfate’s Ability to Relax Mouse Uterus

AI simplified

Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

Magnesium sulfate showed a dose-dependent inhibitory effect on uterine contractions in mice.

Magnesium sulfate was tested on myometrial strips from nonpregnant, mid-pregnant, and term-pregnant mice.
Its effectiveness in reducing spontaneous contractions increased as gestation progressed.
In the presence of oxytocin, magnesium's inhibitory effect on contractions was less pronounced, showing no significant differences across gestational stages.
The rapid onset and reversal of magnesium's effects suggest that it acts on calcium entry from outside the cell.
These findings indicate that magnesium's efficacy as a tocolytic may be influenced by gestational state and hormonal levels.

AI simplified

Magnesium sulfate is used as a tocolytic, but clinical efficacy has been seriously questioned. Our objective was to use controlled ex vivo conditions and known pregnancy stages, to investigate how 2 key factors, hormones and gestation, affect magnesium's tocolytic ability. We hypothesized that these factors could underlie the varying clinical findings around magnesium's efficacy. Myometrial strips were obtained from nonpregnant (n = 10), mid-pregnant (n = 12), and term-pregnant (n = 11) mouse uterus. The strips were mounted in organ baths superfused with oxygenated physiological saline at pH 7.4 and 37 °C. The effect of different concentrations of MgSO(2-20 mM) was examined on spontaneous and oxytocin-induced (0.5-1 nM) contractions. Contractile properties (amplitude, frequency, and area under the curve) were measured before and after application of magnesium. Magnesium sulfate had a dose-dependent inhibitory effect on both spontaneous and oxytocin-induced contractions but was less effective in the presence of oxytocin. In spontaneous contractions, magnesium was more potent as gestation progressed (P < .0001). In the presence of oxytocin, however, there were no significant gestational differences in its effects on contraction. The rapid onset and reversal of magnesium's effects suggest an extracellular action on calcium entry. Taken together, we conclude that magnesium's actions are influenced by both gestational state and hormones, such that, at least in mice, it is least effective in early gestation with oxytocin present and most effective at term in the absence of oxytocin. That magnesium is least effective preterm and oxytocin decreases its effectiveness throughout gestation, may explain its disappointing clinical effects as a tocolytic. 4

Full Text

Full text is available at the source.

View full text (PDF) ↗View full text (HTML) ↗

Gestational and Hormonal Effects on Magnesium Sulfate’s Ability to Inhibit Mouse Uterine Contractility

Abstract

Full Text

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief

Abstract

Full Text

Related papers

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief