Mg2+/Ca2+ sensing inhibits hormone-stimulated Mg2+ uptake in mouse distal convoluted tubule cells

Bapty BW, Dai LJ, Ritchie G, Jirik F, Canaff L, Hendy GN, and Quamme GA: Mg2+/Ca2+ sensing inhibits hormone-stimulated Mg2+ uptake in mouse distal convoluted tubule cells. American Journal of Physiology 275:F353-F360, 1998.

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Abstract The distal convoluted tubule plays a significant role in renal magnesium conservation. An immortalized mouse distal convoluted tubule (MDCT) cell line has been extensively used to study the cellular mechanisms of magnesium transport in this nephron segment. MDCT cells possess an extracellular polyvalent cation-sensing mechanism responsive to Mg21, Ca21, and neomycin. The present studies determined the effect of Mg21/ Ca21 sensing on hormone-mediated cAMP formation and Mg21 uptake in MDCT cells. MDCT cells were Mg21 depleted by culturing in Mg21-free media for 16 h, and Mg21 uptake was measured by microfluorescence after placing the depleted cells in 1.5 mM MgCl2. The mean rate of Mg21 uptake was 164 6 5 nM/s in control MDCT cells. Activation of Mg21/Ca21 sensing with neomycin did not affect basal Mg21 uptake (155 6 5 nM/s). We have previously reported that treatment of MDCT cells with either glucagon or arginine vasopressin (AVP) stimulated Mg21 entry. In the present studies, the addition of extracellular Mg21 or Ca21 inhibited glucagon- and AVP-stimulated cAMP formation and Mg21 uptake in concentration-dependent manner with half-maximal concentrations of ,1.5 and 3.0 mM, respectively. Exogenous cAMP or forskolin stimulated Mg21 uptake in the presence of Mg21/Ca21 sensing activation.We infer from these studies that Mg21/Ca21-sensing mechanisms located in the distal convoluted tubule may play a role in control of distal magnesium absorption.

The distal convoluted
tubule plays a significant role in renal magnesium
conservation. An immortalized mouse distal convoluted tubule
(MDCT) cell line has been extensively used to study the
cellular mechanisms of magnesium transport in this nephron
segment. MDCT cells possess an extracellular polyvalent
cation-sensing mechanism responsive to Mg21, Ca21, and
neomycin. The present studies determined the effect of Mg21/
Ca21 sensing on hormone-mediated cAMP formation and
Mg21 uptake in MDCT cells. MDCT cells were Mg21 depleted
by culturing in Mg21-free media for 16 h, and Mg21 uptake
was measured by microfluorescence after placing the depleted
cells in 1.5 mM MgCl2. The mean rate of Mg21 uptake
was 164 6 5 nM/s in control MDCT cells. Activation of
Mg21/Ca21 sensing with neomycin did not affect basal Mg21
uptake (155 6 5 nM/s). We have previously reported that
treatment of MDCT cells with either glucagon or arginine
vasopressin (AVP) stimulated Mg21 entry. In the present
studies, the addition of extracellular Mg21 or Ca21 inhibited
glucagon- and AVP-stimulated cAMP formation and Mg21
uptake in concentration-dependent manner with half-maximal
concentrations of ,1.5 and 3.0 mM, respectively. Exogenous
cAMP or forskolin stimulated Mg21 uptake in the
presence of Mg21/Ca21 sensing activation.We infer from these
studies that Mg21/Ca21-sensing mechanisms located in the
distal convoluted tubule may play a role in control of distal
magnesium absorption.
intracellular magnesium; magnesium
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