Golgi apparatus is involved in intracellular Ca2+ regulation in epithelial LLC-PK1 cells

Several lines of evidence suggest that the Golgi apparatus is involved in Ca2+ regulation in renal epithelial LLC-PK1 cells. Laser scanning confocal microscopy (LSCM) was employed to establish that a prominent perinuclear region is occupied mainly by the Golgi apparatus in this cell line. LSCM measurements in individual cells with the ionized Ca2+ indicator calcium green revealed that stimulation of LLC-PK1 cells with arginine vasopressin (AVP) resulted in the elevation of ionized Ca2+ levels. However, the vasopressin-induced rise in ionized Ca2+ was attenuated if the Golgi apparatus was disassembled by pretreating the cells with brefeldin A (BFA). Subcellular measurements of total Ca2+ with ion microscopy in cryogenically prepared cells indicated that 1) within 1 min of AVP treatment significant quantities of sequestered Ca2+ were released from the perinuclear Golgi region and 2) the BFA treatment reduced the total Ca2+ stored in the Golgi region. These observations indicate that the Golgi apparatus is sensitive to hormonal stimulation and may play important roles in intracellular Ca2+ regulation in LLC-PK1 cells.