Permeability of fetal membranes to calcium and magnesium: possible role in preterm labour

Abstract

Calcium (Ca(2+)) and magnesium (Mg(2+)) are co-factors in the synthetic activity of a variety of enzymes and in the secretory process. Both the binding to fetal membranes and the diffusion through the membranes of these two cations could be important factors in the synthesis and/or action of prostaglandins and generation of nitric oxide (NO) which are believed to regulate myometrial activity particularly for the induction of labour. In the present study, the permeability to Ca(2+) and Mg(2+) of chorioamniotic membranes obtained from women who had undergone term or preterm labour was examined. Diffusion of Ca(2+) and Mg(2+) were measured using a system of Plexiglas chambers separated by the mounted fetal membrane. Permeability of Mg(2+) and Ca(2+) through fetal membranes was calculated using non-linear regression analysis. The data show highly significant differences in the diffusion of Ca(2+) and Mg(2+) across fetal membranes between preterm and term labour. Transport coefficient K for Ca(2+) was 0.203 h(-1) and 0. 0223 h(-1) in term and preterm labour respectively. The corresponding values for Mg(2+) were -0.017 h(-1) and 0.051 h(-1) respectively. It is proposed that a considerable reduction in Ca(2+) available to myometrium and placenta would result in down-regulation of nitric oxide synthase (NOS) activity and thereby a reduction in NO production. This together with an effect on intracellular Ca(2+) transport resulting from a reduced availability of Mg(2+) would lead to increased myometrial activity in preterm labour.

Transport and biodistribution of dendrimers across human fetal membranes: Implications for intravaginal administration of dendrimer-drug conjugates

“…The fetal membranes allow the passage of small molecules (< 600 Da) like sodium and glucose by simple diffusion but do not readily permit the passage of substances of molecular weight > 1000 Da [59, 60]The amnion and the chorioamnion, behave physicochemically as porous and partially semipermeable membranes and their cell junctions made of desmosomes, gap junctions and occasional tight junctions offering resistance for paracellular transport [59-62]. The human chorion is sieve-like membrane with large water filled extracellular channels and also the intercellular spaces[59, 60]. The transfer by paracellular pathway is more important than the transcellular pathway in the fetal membranes.…”

Transfer of PAMAM dendrimers across human placenta: Prospects of its use as drug carrier during pregnancy

“…Small molecules (less than 600Da) are known to transit the human placenta and reach the fetus by passive diffusion while the passage of substances of molecular weight > 1000 Da may be restricted depending upon whether there are specific receptors on the surface of the syncytiotrophoblast to facilitate the movement of these large molecules, e.g., Immunoglobulin G or Transcobalamin II –B 12 [12-19] . Importance of the drugs transported from the mother to the fetus and its implications for the fetus were recognized by the teratogenic defects induced by thalidomide [20].…”

Relationship between Preterm Labor and Thrombophilic Gene Polymorphism: A Prospective Sequential Cohort Study

“…Several hypotheses have been brought forward. One of them demonstrated that prostaglandins and nitric oxide are partially involved in the regulation of myometrial contractions during premature delivery [4] .…”