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Simultaneous changes of cell volume and cytosolic calcium concentration in macula densa cells caused by alterations of luminal NaCl concentration
Author(s) -
Liu Ruisheng,
Persson A. Erik G.
Publication year - 2005
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2004.078154
Subject(s) - chemistry , macula densa , calcium , cytosol , fura 2 , biophysics , endocrinology , anatomy , biochemistry , biology , renin–angiotensin system , organic chemistry , blood pressure , enzyme
Cell volume and cytosolic Ca 2+ concentration ([Ca 2+ ] i ) were measured in rabbit macula densa (MD) cells loaded with calcein and Fura Red using confocal microscopy. [Ca 2+ ] i was also analysed with Indo‐1 and fura‐2. We used isolated microperfused thick ascending limbs with attached glomerulus. The results showed that when the luminal NaCl concentration (‘NaCl’) was decreased from 35 to 10 m m , the cell volume decreased by 10.4%, and [Ca 2+ ] i increased by 9.5%. This increase was inhibited in Ca 2+ ‐free solution. When luminal [NaCl] was changed from 35 to 135 m m , the cell volume increased by 15.1%, and [Ca 2+ ] i did not change. The cell volume alterations were not different in Ca 2+ ‐free solutions. Using Indo‐1, basal [Ca 2+ ] i in MD cells was 107.8 n m . When luminal [NaCl] was changed from 135 to 10 m m , [Ca 2 ] i increased by 23.5 n m . Using fura‐2, the basal [Ca 2+ ] i in MD cells was 115.3 n m , and when luminal [NaCl] was changed from 135 or 35 to 10 m m , [Ca 2+ ] i change was 30.1 or 10.6 n m , respectively. An increase in [NaCl] caused no change in [Ca 2+ ] i . In Ca 2+ ‐free solution, no change in [Ca 2+ ] i occurred. A stepwise decrease in luminal [NaCl] resulted in a sigmoid increase in [Ca 2+ ] i in MD cells. The steepest part of the curve was between 70 and 10 m m . In conclusion, we found that MD cells have cell volume regulation, and that [Ca 2+ ] i elevation caused by decreased luminal [NaCl] is independent of the cell volume.