Calcium-induced calcium release participates in cell volume regulation of rabbit TALH cells.
Changes of cell volume and intracellular calcium concentration ([Ca(2+)](i)) in immortalized thick ascending limb of Henle's loop (TALH) cells were monitored using confocal laser scanning microscopy and fura-2 fluorescence, respectively. Reduction of the extracellular osmolarity from 600 to 300 mosmol/l induced cell swelling followed by regulatory volume decrease (RVD). Simultaneously, the [Ca(2+)](i) increased transiently. The calcium rise was not observed in calcium-free solution or in the presence of nifedipine, indicating that the change was, in the first place, due to the activation of a calcium influx. Application of ATP or caffeine in isotonic solutions increased transiently the [Ca(2+)](i) which revealed the existence of stores in TALH cells sensitive to inositol-1,4,5 trisphosphate (IP(3)) and ryanodine. To examine the possibility that the calcium influx might induce calcium release, manganese quenching experiments were performed. In hypotonic calcium-free solutions, the decay of the calcium-insensitive and calcium-sensitive fluorescence occurred simultaneously. In the presence of extracellular calcium however, the calcium-sensitive wavelength revealed initial calcium influx followed by a calcium release from intracellular stores. Thus, the calcium influx was a prerequisite for the calcium release. We conclude that calcium-induced calcium release participates in global calcium signalling during RVD of TALH cells.
Tinel
Hanna
H
Bayer AG, PH-R-CVII, Wuppertal, Germany. hanna.tinel.ht@bayer-ag.de
Kinne-Saffran
Evamaria
E
Kinne
Rolf H
RH
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D007038:Hypotonic Solutions / Q000494:pharmacology; D008138:Loop of Henle / Q000166:cytology* / Q000378:metabolism*; D009997:Osmotic Pressure; D011817:Rabbits; D014882:Water-Electrolyte Balance / Q000502:physiology*
D007038:Hypotonic Solutions; D002118:Calcium