Sodium fluoride increases intracellular calcium in rat renal epithelial cell line NRK-52E.
In our previous experiment using rats, fluoride was reported to cause renal calcification, whose mechanism was deduced to be due to an increase in parathyroid hormone (PTH) secretion. However fluoride-induced renal calcification that was independent of PTH has not been understood well in the nephron of fluoride-treated animals. Thus, we examined the effect of sodium fluoride on intracellular calcium mobilization in a normal rat kidney epithelial cell line (NRK-52E cells). The calcium accumulation was found to be remarkably increased by the addition of sodium fluoride (NaF). The elevation of [Ca2+]i was demonstrated to be due to calcium entry through nifedipine-sensitive calcium channels. In addition, fluoride activates phospholipase C, but inositol 1,4,5-triphosphate (IP3) didn't induce Ca2+ release from the endoplasmic reticulum (ER). Moreover, fluoride alone was deduced to enhance the activity of ER-type Ca2+-ATPase. Finally, on the mechanism of fluoride-induced calcium accumulation in NRK-52E cells, fluoride may activate phospholipase C to generate IP3 and diacylglycerol, and these increases can be elucidated to induce calcium entry through dihydropiridine-sensitive calcium channels. Moreover, fluoride was found to stimulate calcium accumulation through ER-type Ca2+-ATPase into the endoplasmic reticulum. The elevation of ER-type Ca2+-ATPase activity by fluoride was elucidated to operate as a regulatory system to protect against abnormally higher increases in cytosolic calcium concentration via an increase of calcium influx into the endoplasmic reticulum.
Murao
H
H
University of Shizuoka, School of Pharmaceutical Sciences, Department of Environmental Biochemistry and Toxicology, Japan.
Sakagami
N
N
Iguchi
T
T
Murakami
T
T
Suketa
Y
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002478:Cells, Cultured; D018118:Chloride Channels / Q000378:metabolism; D004095:Dihydropyridines / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010281:Parathyroid Hormone / Q000494:pharmacology; D051381:Rats; D012969:Sodium Fluoride / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D018118:Chloride Channels; D004095:Dihydropyridines; D010281:Parathyroid Hormone; C038806:1,4-dihydropyridine; D012969:Sodium Fluoride; D010738:Type C Phospholipases; D000252:Calcium-Transporting ATPases; D002118:Calcium