Tight control of exogenous SERCA expression is required to obtain acceleration of calcium transients with minimal cytotoxic effects in cardiac myocytes

Collateral effects of exogenous sarcoendoplasmic reticulum Ca2+ ATPase (SER CA) expression were characterized in neonatal rat and chicken embryo cardia c myocytes, and the conditions required to produce acceleration of Ca2+ tra nsients with minimal toxicity were established. Cultured myocytes were infe cted with adenovirus vector carrying the cDNA of wild-type SERCA1, an inact ive SERCA1 mutant, or enhanced green fluorescence protein under control of the cytomegalovirus promoter. Controls were exposed to empty virus vector. Each group was tested with and without phenylephrine (PHE) treatment. Under conditions of limited calf-serum exposure, the infected rat myocytes manif ested a more rapid increase in size, protein content, and rate of protein s ynthesis relative to noninfected controls. These changes were not accompani ed by reversal to fetal transcriptional pattern (as observed in hypertrophy triggered by PHE) and may be attributable to facilitated exchange with ser um factors. SERCA virus titers >5 to 6 plaque-forming units per cell produc ed overcrowding of ATPase molecules on intracellular membranes, followed by apoptotic death of a significant number of rat but not chicken myocytes. E nhanced green fluorescence protein virus and empty virus also produced cyto toxic effects but at higher titers than SERCA, Expression of exogenous SERC A and enhancement of Ca2+ transient kinetics could be obtained with minimal cell damage in rat myocytes if the SERCA virus titer were maintained withi n 1 to 4 plaque-forming units per cell. Expression of endogenous SERCA was unchanged, but expression of exogenous SERCA was higher in myocytes rendere d hypertrophic by treatment with PHE than in nontreated controls.