title: Effects of acute maternal hyperglycaemia and hyperosmolality on maternofetal transfer of calcium and magnesium across the in situ perfused rat placenta.
abstract: The effects of acute maternal hyperglycaemia and hyperosmolality on maternofetal placental transfer of Ca, Mg and 51Cr-EDTA were investigated in the rat. On day 21 of gestation (term = 23 d) the fetal circulation of the in situ placenta of anaesthetised rats was perfused with a Mg-free Krebs Ringer solution and the unidirectional maternofetal fluxes of Ca (CaJmf) and Mg (MgJmf), and the unidirectional maternofetal clearance of 51Cr-EDTA ((EDTA)Kmf) were determined before and during maternal hyperglycaemia, hyperosmolality and volume expansion, attained by infusing 30% D-glucose, 25% mannitol and 0.9% saline solutions, respectively, into the maternal circulation. MgJmf was significantly reduced during glucose infusion (23.9 +/- 1.2 v 28.2 +/- 1.4 nmol min(-1) g(-1) placenta during control perfusion (mean +/- SEM); p < 0.005) and during mannitol infusion (28.2 +/- 1.0 v 33.5 +/- 1.5 nmol min(-1) g(-1) placenta; p < 0.001). CaJmf and (EDTA)Kmf were not significantly altered by maternal hyperglycaemia or hyperosmolality. There was no significant change in MgJmf during infusion of saline into the maternal circulation. Maternal plasma Na concentration was significantly reduced in both glucose and mannitol infusion experiments, whereas maternal plasma Mg concentration was significantly reduced only during glucose infusion. We postulate that the reduced maternal plasma Na concentration in the glucose and mannitol experiments might decrease MgJmf via alteration of placental Na+/Mg2+ exchange activity.
authors.affiliation: Academic Unit of Child Health, University of Manchester, St. Mary's Hospital, UK. s.m.husain@qmw.ac.uk
authors.forename: S M
authors.initials: SM
authors.lastname: Husain
authors.forename: M Z
authors.initials: MZ
authors.lastname: Mughal
authors.forename: C P
authors.initials: CP
authors.lastname: Sibley
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002857:Chromium / Q000378:metabolism; D016640:Diabetes, Gestational / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006943:Hyperglycemia; D008274:Magnesium / Q000097:blood / Q000378:metabolism; D008353:Mannitol / Q000378:metabolism; D008431:Maternal-Fetal Exchange; D010477:Perfusion; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011248:Pregnancy Complications; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000097:blood; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D002857:Chromium; D008353:Mannitol; D012964:Sodium; D008274:Magnesium; D005947:Glucose; D002118:Calcium