The Mechanism of Cortisol Action in Cultured Rat Heart Cells

Heart cells growing as monolayer cells in tissue culture have the ability to beat (1) . After several day in culture these same cells cease functioning and lose the morphology characteristic of beating cells . This process by which heart cells lose their ability to beat in culture has been described as dedifferentiation (2) . While studying the effect of steroids on beating, McCarl et al . (3) demonstrated that cortisol not only will enhance the per cent of beating in heart cell cultures, but also will re-initiate beating in those cells which have ceased to function . Thus, cortisol restores and maintains the functionally differentiated state of the heart cell in culture . Since cortisol is instrumental in maintaining the differentiated state of heart cells in culture, studies were performed to determine how the hormone controls the beating phenomenon in heart cells . This report is concerned with the effects of cortisol on RNA and protein synthesis in heart cells and their relationship to beating.