Effects of 5-bromo-2'-deoxyuridine on beating heart cell cultures from neonatal hamsters

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Abstract
Primary heart cell cultures from neonatal hamsters yielded a heterogeneous cell population, containing muscle cells undergoing progressive differentiation and non-muscle cells. Addition of 5-bromo-2''-deoxyuridine [BrdUrd], at an early stage, enhanced the formation of beating sheets of differentiated muscle cells. Accumulation of myosin heavy chains and creatine kinase also occurred in the presence of the analogue. To obtain these effects, the analogue was added during the initial rapid growth phase of the cells. Division of the treated cells ceased when the cell numbers approximately doubled. Similar results were obtained with other inhibitors of DNA synthesis. Improved muscle cell cultures can be obtained by preventing non-muscle cells from overgrowing the cultures. One effect caused only by BrdUrd was a large increase in the Ca2+-stimulated ATPase activity which sedimented at low ionic strength. This increase was not due to a greater content of myofibrillar myosin, or to myosin isoenzyme changes, because purified myosin prepared from treated and untreated cultures did not exhibit the increased Ca2+-stimulated ATPase activity.