P-419: Phospholipase C isoforms and differentiation state of cultured human Vascular Smooth Muscle Cells.

Phospholipase C (PLC) plays an important role in cellular signalling. A number of isoforms of PLC exist; PLCγ1 is highly expressed in fetal and neoplastic tissue, while PLCδ1 is present in large amounts in differentiated smooth muscle. The objective of these studies was to examine the effect of conditions affecting differentiation state on patterns of PLC isoform expression in human vascular smooth muscle cells. Human saphenous vein derived smooth muscle cells (HVSMC) were cultured in DMEM containing 15% foetal calf serum. Smooth muscle α-actin (SM α-actin) and PLC isoforms were determined in cell lysates derived from HVSMC (passage 3) by SDS PAGE and Western blotting. Only PLCδ1 and PLCγ1 were detectable in HVSMC, although PLC β1, β3, β4, δ1, δ2, γ1, γ2 were demonstrable in lysates from rat brain. The effect of changing differentiation state on the relative expression of PLCδ1 and PLCγ1 was investigated by serum withdrawal for seven days (SFM), exposure to retinoic acid (10μM) for 72h or exposure to a HMG CoA reductase inhibitor, lovastatin (3μM) for 24h. Western blots were analysed by densitometry. Data are mean±SEM of the % change in protein estimated by densitometry with respect to untreated control HVSMC