Disturbed cooperation of hepatocytes in the rhythm of protein synthesis by chelating agent of cytoplasmic calcium BAPTA-AM

Previously we demonstrated synchronized oscillations of protein synthesis rate in hepatocyte cultures upon accumulation of monosialoganglioside GM1 in the medium or after introduction of exogenous GM1 to the medium. The synchronized oscillations of the protein synthesis rate in dense hepatocyte cultures were blocked 30 min after their treatment with 10-20 muM BAPTA-AM, a chelating agent of cytoplasmic calcium. Enzyme immunoassay for GM1 demonstrated similar amounts of GM1 in the medium conditioned for 3 h by dense hepatocyte cultures pretreated with 20 muM BAPTA-AM for 1 h and in the medium of normal dense cultures: 0.0060+/-0.0005 and 0.0055+/-0.0005 pmol/1000cells, respectively. The content of GM1 was also similar in the normal and BAPTA-AM-pretreated hepatocytes: 0.158+/-0.013 and 0.183+/-0.014 pmol/1000 cells, respectively. The synchronized rhythm of protein synthesis has been confirmed in the diluted cultures in the medium conditioned by the normal dense cultures. However, the medium conditioned by the dense cultures pretreated with BAPTA-AM, induced no synchronization of the diluted cultures. Since GM1 concentration was normal in this medium, we propose the effect of a physicochemical form of the gangliosides accumulated in the medium on their ability to synchronize the rhythm of protein synthesis.