Platelet Derived Growth Factor-BB Induced Calcium Transients in Cultured Human Peritoneal Mesothelial Cells

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The peritoneal membrane is used as an artificial dialysis organ for patients with end-stage renal failure during continuous ambulatory peritoneal dialysis (CAPD). Resident peritoneal mast cells may influence the course of the inflammatory process during acute infection or prolonged exposure to dialysate in a paracrine fashion, with the release of preformed mediators, including platelet derived growth factor (PDGF), which may activate human peritoneal mesothelial cells (HPMC) and other peritoneal cells. PDGF receptor interactions have multiple intracellular effects, typified by cell proliferation, protein synthesis, cytoskeletal organization, extracellular matrix turnover, and angiogenesis. PDGF may mediate HPMC inflammatory response by stimulating cytokine release. The presence of transcripts for both PDGF-B polypeptide and PDGF-β receptor in cultured HPMC was confirmed using a reverse transcriptase-polymerase chain reaction. To investigate the activity of PDGF-β receptors in HPMC, the authors examined intracellular calcium (Cai2+) mobilization in HPMC in response to PDGF-BB (100 ng/ml), histamine (1.0 mmol/L), and 4-brA23187 (1.0 µmol/L) using the calcium indicator, fura-2. HPMC calcium mobilization in response to PDGF was assessed in Krebs-Ringer saline, with and without added external calcium (Ca2+ext). HPMC responded to PDGF with a transient rise in Cai2+ (approximately 1.6-fold) that returned to an elevated resting value. In the absence of Ca2+ext, PDGF produced a Cai2+transient indicative of Ca2+ release from intracellular stores. These results suggest that HPMC have functional PDGF-β receptors that may bind and respond to PDGF in both an autocrine and paracrine fashion.

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