title: [Comparison of the effects of taurine and magnesium on electrical characteristics of artificial and natural membranes. V. Study on the human amnion of the antagonism between magnesium, taurine and polluting metals].
abstract: The effects of metal pollutants (Pb, Cd, Hg, As) were studied on strips of human amnion isolated from the placental zone put in between two Ussing chambers with Hanks' solution at 37 degrees C and pH 7.4. The total conductance Gt through the human isolated amnion was decreased on the fetal side by Pb and As; on the maternal side by Cd, Hg and As. When Gt was decreased by metal pollutants, Mg or taurine (TA) were added in the external medium to induce an antagonism between Mg or TA and metal pollutants. The addition of Mg increased significantly the Gt reduced by Pb, Cd and Hg, but had no effect on the Gt reduced by As. The addition of taurine increased significantly the Gt reduced by Cd and Hg, but had no effect on the Gt reduced by Pb and As. Dixon's kinetics (Gt as a function of the Mg or TA concentration when the metal pollutant concentration increased) indicate that there is a competitive inhibition between Mg-Pb and Mg-Cd (the inhibition constant Ki is lower with Pb (= 2.5) than with Cd (= 11.4) and suggests a greater antagonism between Mg-Pb than between Mg-Cd). Moreover, there appears to be a noncompetitive inhibition between Mg-Hg, TA-Cd and TA-Hg. These results indicate that Mg and TA, on the fetal side, exert an action on the same sites and that, on the maternal side, their action takes place on the same sites and also on different ones. Also, TA can be considered as a partial magnesium agonist, at least in the human amnion.
mesh_terms: D000393:Air Pollutants; D000650:Amnion / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D001151:Arsenic / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002104:Cadmium / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D005260:Female; D005333:Fetus / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D007854:Lead / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology*; D008628:Mercury / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011247:Pregnancy; D013654:Taurine / Q000494:pharmacology*
chemical_list: D000393:Air Pollutants; D002104:Cadmium; D013654:Taurine; D007854:Lead; D008628:Mercury; D008274:Magnesium; D001151:Arsenic
vernacular_title: Comparaison des effets de la taurine et du magnésium sur les caractéristiques électriques de diverses membranes artificielles et naturelles. V. Etude sur l'amnios humain, de l'antagonisme entre magnésium, taurine et métaux polluants.