Aldosterone and Cortisol Acutely Stimulate Na⁺/H⁺ Exchanger Activity in the Syncytiotrophoblast of the Human Placenta: Effect of Fetal Sex

(A) Experimental protocol for the measurement of recovery from an acid load in the syncytiotrophoblast of the isolated human placental villous. All procedures were performed at 37 °C and arrows indicate solution changes. Tissue was loaded with BCECF (see methods) and incubated in control Tyrode's buffer then switched to Tyrode's buffer containing 20 mM NH₄Cl (substituted for 20 mM NaCl) for 5 min. The incubating medium was then changed to a Na⁺-free solution (choline substituted for Na⁺) for 3 min before being returned to normal Na⁺ containing Tyrode's buffer. Compounds (aldo = aldosterone, cort = cortisol, carbenx = carbenoxolone) under investigation were added to the medium for the Na⁺ free period and the recovery phase when the tissue was returned to normal Na⁺ Tyrode's buffer as indicated by the bars above the experimental trace. MR = mineralocorticoid receptor, GR = glucocorticoid receptor (B) To calculate the initial recovery rate, a linear regression was applied to the first 30 s of the recovery phase post acid load and Na⁺ free period dashed line.

Recovery of syncytiotrophoblast [pH]_i following acid loading by a 20 mM NH₄Cl pulse in the absence (control) or in the presence of aldosterone (10 nM). Open bars represent placenta from male babies, closed bars represent placenta from female babies and the bars are mean + SEM with n (in brackets) = number of placentas. *p < 0.05 versus control: paired Student's t-test.

Recovery of syncytiotrophoblast [pH]_i in placentas from female babies following acid loading by a 20 mM NH₄Cl pulse in the absence (control), or presence of aldosterone (10 nM) and also in the presence of spironolactone (spir, 1 μM) or mifepristone (mif, 1 μM). Bars are mean + SEM with n (in brackets) = number of placentas. *p < 0.05, **p < 0.01 versus control, #p < 0.05 versus aldosterone alone: ANOVA followed by Bonferroni's post hoc test.

Recovery of syncytiotrophoblast [pH]_i following acid loading by a 20 mM NH₄Cl pulse (a) in the absence (control) or in the presence of carbenoxolone (100 μM) or (b) cortisol (1 μM), or (c) combined application of cortisol (1 μM) and carbenoxolone (100 μM). Bars represent mean + SEM with n (in brackets) = number of placentas. *p < 0.05 versus control: paired Student's t-test.

Recovery of syncytiotrophoblast [pH] _i following acid loading by a 20 mM NH₄Cl pulse in the absence (control) or in the presence of a combined application of cortisol (1 μM) and carbenoxolone (100 μM). Open bars represent placenta from male babies, closed bars represent placenta from female babies and the bars are mean + SEM with n (in brackets) = number of placentas. *p < 0.05 versus control: paired Student's t-test comparing experiments performed on the same placentas (n = 9).

Recovery of syncytiotrophoblast [pH]_i in placentas from female babies following acid loading by a 20 mM NH₄Cl pulse in the absence (control), in the presence of a combined application of cortisol (1 μM) and carbenoxolone (100 μM) and also in the presence of spironolactone (spir, 1 μM) or mifepristone (mif, 1 μM). Bars are mean + SEM with n = 8 placentas. *p < 0.05 versus control, #P < 0.05 versus cortisol/carbenoxolone: ANOVA followed by Bonferroni's post hoc test.