[Heart ventricular cells of neonatal rats in a culture: DNA synthesis, ultrastructure and localization of atrial natriuretic peptide].

We determined the optimal conditions suitable for expanding cardiac cells in vitro for their future use in experimental transplantation into injured myocardium of adult animals. Ventricular cardiac cells were isolated enzymatically from 2-3 day-old rats and cultured at different cell densities within 5-7 days to 4 weeks. Mixed cultures of muscle and non-muscle cells were examined by light autoradiography, electron microscopy, and immunogold method. The best results were obtained at a density of 3 x 10(5) cells/ml in the medium, consisting of 90% DMEM and 10% fetal calf serum, during 5-7 days of cultivation. In such cultures myocytes made 62.5 +/- 7.9%. After a 24 h incubation with 3H-thymidine, 22.0 +/- 2.2% of myocytes were labeled. Muscle cells contact with each other and with non-muscle cells, contain myofibrils, contract and display atrial natriuretic peptide (ANP)-like immunoreactivity.