Published in:
01-06-2012 | Original Article
Characteristics of spontaneous calcium oscillations in renal tubular epithelial cells
Published in: Clinical and Experimental Nephrology | Issue 3/2012
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Background
The kidney is a major organ involved in calcium (Ca2+) metabolism. Ca2+ is transported through renal tubular epithelial cells. The intracellular free calcium concentration ([Ca2+]i) is tightly controlled at a low concentration, but transient increases and oscillations in [Ca2+]i are induced by various conditions. In this study, we investigated the mechanisms underlying the spontaneous [Ca2+]i oscillations observed in MDCK cells.
Methods
[Ca2+]i was monitored in fura-2-loaded Madin-Darby canine kidney (MDCK) cells using a calcium imaging system. We investigated the mechanism by which [Ca2+]i changed by applying drugs or by changing the extracellular Ca2+ concentration.
Results
Spontaneous [Ca2+]i oscillations occurred in MDCK cells. The oscillations occurred irregularly and were not transmitted to neighboring cells. Spontaneous [Ca2+]i oscillations in MDCK cells were initiated by Ca2+ release from ryanodine/IP3-sensitive intracellular calcium stores, and their frequency was largely unaffected by the extracellular Ca2+ concentration. Moreover, the frequency of the oscillations was increased by extracellular nucleotide, but was decreased when the nucleotides were removed.
Conclusions
Our study suggested that [Ca2+]i release from ryanodine/IP3-sensitive intracellular calcium stores mediates spontaneous [Ca2+]i oscillations in MDCK cells. Calcium oscillations may be associated with the function of the renal tubular epithelial cells.