Regulation of growth of newborn rat heart cell cultures: influence of cell density, pH, and a platelet-derived factor.

The search for elements regulating cardiac cell growth was undertaken using heart cell cultures as a model system. This model, derived from newborn rats, allowed the approach of the regulation of growth both at the cellular level and at a stage of incomplete differentiation of the muscle cells. The major control elements that have been identified are: 1) availability of essential nutrients; 2) proper regulation of the pH in the surrounding medium; 3) presence of serum survival factors and serum growth factors; and 4) homotypic and heterotypic cellular interactions. Specific examples pertaining to these different control elements are presented.