Aldosterone potentiates hormone-stimulated Mg2+ uptake in mouse distal convoluted tubule cells

Dai LJ, Ritchie G, Bapty BW, and Quamme GA: Aldosterone potentiates hormone-stimulated  Mg2+ uptake in mouse distal convoluted tubule cells. American Journal of Physiology 274:F336-F341, 1998.

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Abstract The distal convoluted tubule reabsorbs significant amounts of filtered magnesium that is under hormonal control. In this study, we describe the effects of aldosterone on Mg21 uptake in an immortalized mouse distal convoluted tubule (MDCT) cell line. Intracellular free Mg21 concentration ([Mg21]i) was determined on single MDCT cells using microfluorescence with mag-fura 2. To determine Mg21 entry rate into MDCT cells, they were first Mg21 depleted ([Mg21]i, 0.22 6 0.01 mM) by culturing in Mg21-free media for 16 h and then placed in 1.5mMMgCl2. The rate of change in [Mg21]i as measured as a function of time, d([Mg21]i)/dt, was 164 6 5 nM/s in control cells. We have shown that glucagon or arginine vasopressin (AVP) stimulates Mg21 entry by 63% and 15%, respectively. Incubation of MDCT cells with aldosterone for 16 h did not change the rate of Mg21 uptake (172 6 8 nM/s). However, aldosterone potentiated glucagon- and AVP-stimulated Mg21 uptake rate up to 330 6 39 and 224 6 6 nM/s, respectively. Aldosterone also potentiated glucagon- and AVP-induced intracellular cAMP accumulation in a concentration-independent manner. As cAMP stimulates Mg21 entry in MDCT cells, it is inferred that aldosterone may stimulate Mg21 uptake through intracellular signaling pathways involving cAMP. The actions of aldosterone were dependent on de novo protein synthesis, as pretreatment of the cells with cycloheximide inhibited aldosterone potentiation of hormone stimulation of Mg21 uptake and cAMP accumulation. These studies with MDCT cells suggest that aldosterone may modulate the effects of hormones acting within the distal convoluted tubule to control magnesium absorption.

distal convoluted tubule reabsorbs significant amounts of
filtered magnesium that is under hormonal control. In this
study, we describe the effects of aldosterone on Mg21 uptake
in an immortalized mouse distal convoluted tubule (MDCT)
cell line. Intracellular free Mg21 concentration ([Mg21]i) was
determined on single MDCT cells using microfluorescence
with mag-fura 2. To determine Mg21 entry rate into MDCT
cells, they were first Mg21 depleted ([Mg21]i, 0.22 6 0.01 mM)
by culturing in Mg21-free media for 16 h and then placed in
1.5mMMgCl2. The rate of change in [Mg21]i as measured as a
function of time, d([Mg21]i)/dt, was 164 6 5 nM/s in control
cells. We have shown that glucagon or arginine vasopressin
(AVP) stimulates Mg21 entry by 63% and 15%, respectively.
Incubation of MDCT cells with aldosterone for 16 h did not
change the rate of Mg21 uptake (172 6 8 nM/s). However,
aldosterone potentiated glucagon- and AVP-stimulated Mg21
uptake rate up to 330 6 39 and 224 6 6 nM/s, respectively.
Aldosterone also potentiated glucagon- and AVP-induced
intracellular cAMP accumulation in a concentration-independent
manner. As cAMP stimulates Mg21 entry in MDCT cells,
it is inferred that aldosterone may stimulate Mg21 uptake
through intracellular signaling pathways involving cAMP.
The actions of aldosterone were dependent on de novo protein
synthesis, as pretreatment of the cells with cycloheximide
inhibited aldosterone potentiation of hormone stimulation of
Mg21 uptake and cAMP accumulation. These studies with
MDCT cells suggest that aldosterone may modulate the
effects of hormones acting within the distal convoluted tubule
to control magnesium absorption.
intracellular magnesium; fluorescence
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