PDGF-BB, BUT NOT PDGF-AA, STIMULATES CALCIUM MOBILIZATION, ACTIVATIONOF CALCIUM CHANNELS AND CELL-PROLIFERATION IN CULTURED RAT MESANGIAL CELLS

The effects of different isoforms of platelet-derived growth factor (P DGF) on cellular growth and on cytoplasmic Ca2+ levels in mesangial ce lls using a microfluorometric system and the calcium indicator FURA-2 were investigated. A rapid increase of cytoplasmic calcium in response to PDGF-BB was found and in the presence of 1.25 mM extracellular cal cium, the resting level of cytoplasmic calcium following the initial p eak was significantly increased compared with a calcium-free medium, b ut was completely attenuated with the calcium channel blocker verapami l (50 muM). PDGF-AA did not cause any increase in cytoplasmic calcium. In growth arrested MC PDGF-BB, but not PDGF-AA, also enhanced cell gr owth. It is concluded that cultured rat mesangial cells react to PDGF- BB but not to PDGF-AA with a rapid mobilization of intracellular calci um followed by subsequent activation of calcium channels and a stimula tion of cell growth. A PDGF-BB driven mechanism for MC proliferation i n inflammatory and metabolic glomerular diseases is suggested.