Effects of furosemide on renal calcium handling.
Furosemide is a loop diuretic agent that has been used to treat hypercalcemia because it increases renal calcium excretion. The effect of furosemide on calcium transport molecules in distal tubules has yet to be investigated. We conducted studies to examine the effects of furosemide on renal calcium excretion and expression of calcium transport molecules in mice. Mice were administered with a single dose of furosemide (15 mg/kg) and examined 4 h later or were given twice-daily furosemide injections for 3 days. To evaluate the effects of volume depletion, drinking water was supplemented with salt. Our results showed that, in acute experiments, furosemide enhanced urinary calcium excretion, which was associated with a significant increase in mRNA levels of TRPV5, TRPV6, and calbindin-D28k but not calbindin-D9k as measured by real-time PCR (TRPV5 and TRPV6 are transient receptor potential vanilloid 5 and 6). Chronic furosemide administration induced three- to fourfold increases in urinary calcium excretion and elevated mRNA levels of TRPV5, TRPV6, calbindin-D28k, and calbindin-D9k without or with salt supplement. Similar upregulation of calcium transport molecules was observed in mice with gentamicin-induced hypercalciuria. Coadministration of chlorothiazide decreased furosemide-induced calciuria, either acutely or chronically, although still accompanied by upregulation of these transport molecules. Immunofluorescent staining studies revealed comparably increased protein abundance in TRPV5 and calbindin-D28k. We conclude that furosemide treatment enhances urinary calcium excretion. Increased abundance of calcium transport molecules in the distal convoluted tubule represents a solute load-dependent effect in response to increased calcium delivery and serves as a compensatory adaptation in the downstream segment.
Lee
Chien-Te
CT
Division of Nephrology, Department of Medicine, Chang-Gung Memorial Hospital, Kaohsiung Medical Center, Chang-Gung University College of Medicine, Kaohsiung, Taiwan.
Chen
Hung-Chun
HC
Lai
Li-Wen
LW
Yong
Kim-Chong
KC
Lien
Yeong-Hau H
YH
D000818:Animals; D064092:Calbindin 1; D064026:Calbindins; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D004232:Diuretics / Q000494:pharmacology*; D005665:Furosemide / Q000494:pharmacology*; D005839:Gentamicins / Q000494:pharmacology; D007686:Kidney Tubules, Distal / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D050916:TRPV Cation Channels / Q000378:metabolism; D049971:Thiazides / Q000494:pharmacology
C576499:Calb1 protein, mouse; D064092:Calbindin 1; D064026:Calbindins; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D004232:Diuretics; D005839:Gentamicins; D064030:S100 Calcium Binding Protein G; C576507:S100g protein, mouse; D050916:TRPV Cation Channels; D049971:Thiazides; C492240:Trpv5 protein, mouse; C446923:Trpv6 protein, mouse; D005665:Furosemide; D002118:Calcium