2-O-methyl PAF as a Ca2+ mobilizer in Madin Darby canine kidney cells.
In Madin-Darby canine kidney (MDCK) cells, the effect of 2-O-methyl PAF, an inactive analogue of platelet activating factor (PAF), on intracellular Ca2+ concentration ([Ca2+]i) was measured by using the Ca2+-sensitive fluorescent dye fura-2. 2-O-methyl PAF (> or = 15 microM) caused a rapid rise of [Ca2+]i in a concentration-dependent manner. 2-O-methyl PAF-induced [Ca2+]i rise was partly reduced by removal of extracellular Ca2+. 2-O-methyl PAF-induced extracellular Ca2+ influx was also suggested by Mn2+ influx-induced fura-2 fluorescence quench. The 2-O-methyl PAF-induced Ca2+ influx was blocked by nifedipine, verapamil and diltiazem. In Ca2+-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+-ATPase, caused a monophasic [Ca2+]i rise, after which 2-O-methyl PAF failed to increase [Ca2+]i; also, pretreatment with 2-O-methyl PAF depleted thapsigargin-sensitive Ca2+ stores. U73122, an inhibitor of phospholipase C, abolished ATP (but not 2-O-methyl PAF)-induced [Ca2+]i rise. These findings suggest that 2-O-methyl PAF evokes a rapid increase in [Ca2+]i in renal tubular cells by stimulating both extracellular Ca2+ influx and intracellular Ca2+ release.
Yeh
Jeng-Hsien
JH
Department of Pathology and Laboratory Medicine, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan 813.
Huang
Chun-Jen
CJ
Lee
Jang-Hwa
JH
Hsu
Shu-Shong
SS
Chen
Jin-Shyr
JS
Cheng
He-Hsiung
HH
Chang
Hong-Tai
HT
Huang
Jong-Khing
JK
Chung
Hsiao-Min
HM
Mei-Yin
Yeh
Y
Jan
Chung-Ren
CR
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D004285:Dogs; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000031:analogs & derivatives* / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism
D005456:Fluorescent Dyes; D010972:Platelet Activating Factor; D010738:Type C Phospholipases; D002118:Calcium; D016257:Fura-2