Mechanisms of diethylstilbestrol-induced calcium movement in MG63 human osteosarcoma cells.
The effect of the estrogen diethylstilbestrol (DES) on cytosolic free Ca(2+) levels ([Ca(2+)](i)) in MG63 human osteoblasts was explored by using fura-2 as a Ca(2+) indicator. DES at concentrations between 5--20 microM induced an immediate increase in [Ca(2+)](i) in a concentration-dependent manner with an EC(50) of 10 microM. Removing extracellular Ca(2+) reduced the Ca(2+) signal by 70%. Pretreatment with 50 microM La(3+) or 10 microM of nifedipine, verapamil and diltiazem did not change 20 microM DES-induced [Ca(2+)](i) increases. Addition of 3 mM Ca(2+) increased [Ca(2+)](i) in cells pretreated with 20 microM DES in Ca(2+)-free medium. Pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor) to deplete the endoplasmic reticulum Ca(2+) store partly inhibited 20 microM DES-induced Ca(2+) release, but addition of carbonylcyanide m-chlorophenylhydrazone (CCCP; a mitochondrial uncoupler) and thapsigargin together abolished DES-induced Ca(2+) release. Conversely, pretreatment with 20 microM DES abrogated CCCP- and thapsigargin-induced Ca(2+) release. Inhibition of phospholipase C activity with 2 microM U73122 did not alter 20 microM DES-induced Ca2+ release. Another estrogen 17beta-estradiol also increased [Ca(2+)](i) in a concentration-dependent manner with an EC50 of 7 microM. Together, the data indicate that in human osteoblasts, DES increased [Ca(2+)](i) via causing Ca(2+) release from both mitochondria and the endoplasmic reticulum in a phospholipase C-independent manner, and by causing Ca(2+) influx.
Chen
Y C
YC
Department of Orthopaedic Surgery, Chang-Gung Memorial General Hospital, Kaohsiung, Taiwan.
Chen
S J
SJ
Chang
H T
HT
Huang
J K
JK
Wang
J L
JL
Tseng
L L
LL
Chang
H J
HJ
Su
W
W
Law
Y P
YP
Chen
W C
WC
Jan
C R
CR
D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004054:Diethylstilbestrol / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D007811:Lanthanum / Q000494:pharmacology; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D012516:Osteosarcoma / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism
D002121:Calcium Channel Blockers; D004958:Estradiol; D007811:Lanthanum; D004054:Diethylstilbestrol; D010738:Type C Phospholipases; D002118:Calcium; D016257:Fura-2