[Comparison of the effects of taurine and magnesium on electrical characteristics of artificial and natural membranes. IV. Effects on different components of the paracellular and cellular conductances of the human amnion].

The ionic conductance, Gt, through the isolated human amnion is the sum of several conductances: Gt = Gp + Gc + Gs. Gp, the paracellular conductance is: Gp = Gj + Gjc (Gj is due to the intercellular channel and Gjc due to the electrical coupling factor); Gc, the cellular conductance is: Gc = Gc1. Gc2/Gc1 + Gc2 with Gc1 = GAC + GAC1 and Gc2 = GM + GM1, GAC and GM being the dependent conductances on amniotic cavity (AC) and maternal (M) sides; GAC1 and GM1 being the leak conductances on AC and M. Gp and Gc are due to epithelial cell layer and Gs (conductance in a series) is due to the other layers. The utilization of metabolic inhibitors (ouabain, amiloride, DNP) allows one to split up Gt into various components. In this study, the action of magnesium and taurine (TA) was studied on the various conductances in Hanks' solution modified by metabolic inhibitors. In Hanks' solution: + ouabain, Mg and TA increased GAC1 and GM1; - + amiloride, Mg increased GAC and GM but TA had no effect; - + ouabain + amiloride, Mg and TA increased GK. In this way, Mg appears to have an action on the ATPase and on the regulation of the Na+ and K+ channels, but TA has no effect on the ATPase but TA appears to govern the viability of the Na+ and K+ channels. Moreover, TA and Mg have a compensatory effect on GAC1, GM1 and Gjc in Hanks' solution, but their actions are not cumulative.