Different profiles of Ca2+ responses to endothelin-1 and PDGF in liver myofibroblasts during the process of cell differentiation.
OBJECTIVE
Hepatic stellate cells play an important role in liver fibrosis but little is known about liver myofibroblasts located around the central vein and in the portal area. In this study, intracellular Ca(2+) concentration ([Ca(2+)](i)) was measured to assess the response to endothelin-1 (ET-1), platelet derived growth factor (PDGF) and ATP in rat liver myofibroblasts.


METHODS
Rat liver myofibroblasts were compared in 'quiescent' (cultured on Matrigel-coated dishes) and 'activated' (cultured on non-coated plastic dishes) conditions. [Ca(2+)](i) was measured with the fluorescent dye fura-2 and mRNA for ET-1, PDGF and their receptors by RT-PCR.


RESULTS
ET-1 increased [Ca(2+)](i) in quiescent cells but not in activated cells, whereas PDGF-BB increased [Ca(2+)](i) in activated cells but not in quiescent cells. However, there was no difference between responses to ATP in quiescent or activated cells. ET-1 (in quiescent cells), PDGF-BB (in activated cells) and ATP (in both cells) all induced transient increases in [Ca(2+)](i) in the absence of extracellular Ca(2+) (with EGTA), indicating the involvement of Ca(2+) release from intracellular Ca(2+) stores. The sustained increase in [Ca(2+)](i) in the presence of external Ca(2+) in activated cells (ATP and PDGF) was significantly reduced by nicardipine, a L-type Ca(2+) channel blocker, but not in quiescent cells (ATP and ET-1).


CONCLUSIONS
The different pharmacological profiles of [Ca(2+)](i)-response in quiescent and activated myofibroblasts suggest that ET-1 and PDGF contribute differently to myofibroblast activation during the process of liver fibrosis.
Kojima
N
N
Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Hori
M
M
Murata
T
T
Morizane
Y
Y
Ozaki
H
H
D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D000077214:Becaplermin; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000502:physiology*; D005347:Fibroblasts / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008103:Liver Cirrhosis / Q000503:physiopathology*; D008297:Male; D010982:Platelet-Derived Growth Factor / Q000502:physiology*; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction
D019332:Endothelin-1; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D000077214:Becaplermin; D000255:Adenosine Triphosphate; D002118:Calcium