Ca2+ Regulatory Protein Levels Altered in Cultured VSMC Grown in High Glucose. Immunoblots of the SERCA and IP3R isoforms in cytoplasmic and nuclear extracts from A7r5 cells grown in high or medium glucose concentrations are shown. SERCA2 protein levels remained steady in the cytoplasm, but an increase was observed in the nuclear extract from cells in high glucose. SERCA3 in the cytoplasm was detected at equally low levels in either glucose concentration. Nuclear SERCA3 levels were reduced with hyperglycemic treatment. All IP3Rs showed a reduction in protein levels in response to high glucose.