Effects of low density lipoprotein on cytosolic [Ca++] in cultured rat mesangial cells.
BACKGROUND
Recently, a low density lipoprotein (LDL) receptor has been identified in mesangial cells. However, the nature of intracellular signals in mesangial cells after exposure to LDL is unclear.


METHODS
We studied the effect of LDL on cultured rat mesangial cell [Ca++]i using spectrofluorometry.


RESULTS
Addition of LDL (15 micrograms/mL) produced a rapid, transient, and dose-dependent rise in [Ca++]i within seconds, returning to baseline in 6 minutes. No further rise was observed at higher LDL concentrations. No significant rise in [Ca++]i was observed with LDL in cells placed in a Ca(++)-free medium. The [Ca++]i rise was greatly attenuated in magnitude and duration when lanthanum was used. In contrast, verapamil failed to block the LDL-induced rise in [Ca++]i. Addition of LDL did not alter production of inositol 1,4,5-triphosphate (IP3) by mesangial cells.


CONCLUSIONS
Low density lipoprotein caused a transient rise in [Ca++]i in cultured rat mesangial cells. The observed rise in [Ca++]i was largely caused by influx of extracellular Ca++ through receptor-gated channels. Mobilization from intracellular stores and activation of IP3 were not involved. The rise in [Ca++]i may mediate the effects of LDL on mesangial cell function.
Pahl
M V
MV
Department of Medicine, University of California, Irvine Medical Center 92668, USA.
Wang
J
J
Zhou
X J
XJ
Wang
X Q
XQ
Tehranzadeh
A
A
Vaziri
N D
ND
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects*; D002478:Cells, Cultured; D003600:Cytosol; D004305:Dose-Response Relationship, Drug; D005920:Glomerular Mesangium / Q000187:drug effects* / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013050:Spectrometry, Fluorescence
D015220:Calcium Channels; D008077:Lipoproteins, LDL; D015544:Inositol 1,4,5-Trisphosphate