Extracellular Mg2+-and Ca2+-sensing in mouse distal convoluted tubule cells

greedy — Thu, 17 Sep 2009 22:38:38 +0000

Bapty BW, Dai LJ, Ritchie G, Jirik F, Canaff L, Hendy GN, and Quamme GA: Extracellular Mg²⁺-and Ca²⁺-sensing in mouse distal convoluted tubule cells. Kidney International 53:583-592, 1998.

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Abstract An immortalized cell line (designated MDCT) has been extensively used to investigate the cellular mechanisms of electrolyte transport within the mouse distal convoluted tubule. Mouse distal convoluted tubule cells possess many of the functional characteristics of the in vivo distal convoluted tubule. In the present study, we show that MDCT cells also possess a polyvalent cation-sensing mechanism that is responsive to extracellular magnesium and calcium. Southern hybridization of reverse transcribed-polymerase chain reaction (RT-PCR) products, sequence determination and Western analysis indicated that the calcium-sensing receptor (Casr) is expressed in MDCT cells. Using microfluorescence of single MDCT cells to determine cytosolic Ca21 signaling, it was shown that the polyvalent cation-sensing mechanism is sensitive to extracellular magnesium concentration ([Mg21]o) and extracellular calcium concentration ([Ca21]o) in concentration ranges normally observed in the plasma. Moreover, both [Mg21]o and [Ca21]o were effective in generating intracellular Ca21 transients in the presence of large concentrations of [Ca21]o and [Mg21]o, respectively. These responses are unlike those observed for the Casr in the parathyroid gland. Finally, activation of the polycationsensitive mechanism with either [Mg21]o or [Ca21]o inhibited parathyroid hormone-, calcitonin-, glucagon- and arginine vasopressin-stimulated cAMP release in MDCT cells. These studies indicate that immortalized MDCT cells possess a polyvalent cation-sensing mechanism and emphasize the important role this mechanism plays in modulating intracellular signals in response to changes in [Mg21]o as well as in [Ca21]o.

An immortalized cell line (designated MDCT) has been

extensively used to investigate the cellular mechanisms of electrolyte

transport within the mouse distal convoluted tubule. Mouse distal convoluted

tubule cells possess many of the functional characteristics of the in

vivo distal convoluted tubule. In the present study, we show that MDCT

cells also possess a polyvalent cation-sensing mechanism that is responsive

to extracellular magnesium and calcium. Southern hybridization of reverse

transcribed-polymerase chain reaction (RT-PCR) products, sequence

determination and Western analysis indicated that the calcium-sensing

receptor (Casr) is expressed in MDCT cells. Using microfluorescence of

single MDCT cells to determine cytosolic Ca21 signaling, it was shown

that the polyvalent cation-sensing mechanism is sensitive to extracellular

magnesium concentration ([Mg21]o) and extracellular calcium concentration

([Ca21]o) in concentration ranges normally observed in the plasma.

Moreover, both [Mg21]o and [Ca21]o were effective in generating intracellular

Ca21 transients in the presence of large concentrations of [Ca21]o

and [Mg21]o, respectively. These responses are unlike those observed for

the Casr in the parathyroid gland. Finally, activation of the polycationsensitive

mechanism with either [Mg21]o or [Ca21]o inhibited parathyroid

hormone-, calcitonin-, glucagon- and arginine vasopressin-stimulated

cAMP release in MDCT cells. These studies indicate that immortalized

MDCT cells possess a polyvalent cation-sensing mechanism and emphasize

the important role this mechanism plays in modulating intracellular

signals in response to changes in [Mg21]o as well as in [Ca21]o.

Dr. Long Jun Dai » Kidney International

Extracellular Mg2+-and Ca2+-sensing in mouse distal convoluted tubule cells