2-O-methyl PAF as a Ca2+ mobilizer in Madin Darby canine kidney cells

摘要

In Madin-Darby canine kidney (MDCK) cells, the effect of 2-0-methyl PAT, 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 (>= 15 mu M) 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. (c) 2005 Published by Elsevier Inc.