Abstract.
The effect of extracellular calcium ([Ca2+] e ) on cytosolic calcium ([Ca2+] i ) was investigated in thick ascending limbs and collecting ducts from the rat kidney, using the fluorescent dye fura-2. In cortical collecting ducts, basolateral but not apical changes in [Ca2+] e were associated with parallel changes in [Ca2+] i . Basal [Ca2+] i was hardly modified by nifedipine and verapamil but was decreased by 60% by basolateral La3+. Increasing peritubular [Ca2+] e triggered Ca2+ release from intracellular stores. This effect was not reproduced by agonists of the renal Ca2+-receptor RaKCaR, e.g., Ba2+, Mg2+, Gd3+, and neomycin, but was reproduced by Ni2+. Ni2+-induced mobilization of intracellular Ca2+ was larger in the inner medullary collecting duct, a segment which poorly responds to increasing [Ca2+] e .
In the cortical thick ascending limb, removing basolateral Ca2+ hardly altered [Ca2+] i but increasing [Ca2+] e or adding Ba2+, Mg2+, Gd3+ and neomycin released intracellular calcium.
These data demonstrate that (1) basolateral influx of calcium occurs in cortical collecting ducts, under basal conditions; (2) this influx occurs through nonvoltage gated channels, permeable to Ba2+, insensitive to verapamil and nifedipine, and blocked by La3+; (3) increasing [Ca2+] e stimulates the influx and triggers intracellular calcium release, independently of the phospholipase C-coupled receptor RaKCaR; (4) RaKCaR is functionally expressed in thick ascending limbs; (5) another membrane receptor, sensitive to Ni2+ but not to Ca2+ is present in the collecting duct.
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Received: 12 July 1996/Revised: 28 October 1996
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Champigneulle, A., Siga, E., Vassent, G. et al. Relationship between Extra- and Intracellular Calcium in Distal Segments of the Renal Tubule. Role of the Ca2+ Receptor RaKCaR . J. Membrane Biol. 156 , 117 –129 (1997). https://doi.org/10.1007/s002329900194
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DOI: https://doi.org/10.1007/s002329900194