ISSN:
1432-1424
Keywords:
Key words: Rat kidney — Fura-2 fluorescence — Cytosolic calcium — Single tubule — Thick ascending limb — Collecting duct — Ca2+ receptor
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002329900194
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