Phosphodiesterase Activity Is Necessary But Not Sufficient For cAMP Compartmentation In Cardiac Myocytes

Abstract

phthalate (DEHP) is a widely used plasticizer found in a variety of polyvinyl chloride (PVC) medical products. The results of studies in experimental animals suggest that DEHP leached from flexible PVC tubing may cause health problems in some patient populations. While the cancerogenic and reproductive effects of DEHP are well recognized, little is known about the potential adverse impact of phthalates on the heart. This study used preparations of confluent, synchronously beating cultures of neonatal rat cardiomyocytes to examine possible adverse effects of clinically relevant concentration of DEHP on cardiac tissue. Seventy two hour-long exposure to 50 mg/ml DEHP led to a marked decrease in conduction velocity and asynchronous cell beating in DEHP-treated samples but not in time-matched controls. The mechanism behind DEHP-induced changes was a loss of junctional connexin-43, documented using western blot analysis, dye-transfer assay and immunofluorescence. Use of organelle-specific connexin-43 antibodies, IF1 and CT1, allowed for further analysis of changes in intracellular distribution of connexin-43. In DEHPtreated samples the amount of gap-junctional connexin-43 (IF1-sensitive) was significantly decreased as compared to the controls. In contrast, Golgi and perinuclear (CT1-sensitive) staining was more pronounced. The data suggests that DEHP modifies connexin-43 trafficking and protein assembly into functional gap junctions, which impairs the electrical behavior of a cardiac cell network. Applicability of these findings to human patients remains to be established.