Heat‐shock response of rat hepatoma variant cells

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Abstract
The effect of mild heat shock on protein synthesis was examined in differentiated and dedifferentiated, glucocorticoid‐sensitive and resistant clones of H4IIEC3 rat hepatoma cells by one‐ and two‐dimensional gel electrophoresis of [35S]methionine‐labeled proteins. Among the major heat‐shock proteins, five were induced in all hepatoma clones. Certain members of the HSP70 family and the corresponding mRNAs were only slightly inducible in the glucocorticoid‐resistant variants, but were strongly inducible in the sensitive ones. Three other proteins lacked heat inducibility in the dedifferentiated clones. The constitutive level of one major heat‐shock protein was elevated in all dedifferentiated variants. These results show that the stage of differentiation influences the expression of heat‐shock genes of hepatoma cells. We found no correlation between the elevated constitutive or induced level of heat‐shock proteins and heat resistance.