Osmotic shock of cultured primary mammary cells amplifies the hormonal induction of casein gene expression.

ABSTRACT

Primary cells from rabbit mammary gland cultured on floating collagen were transfected with various plasmids in different conditions. Conventional transfection methods using DEAE-dextran or calcium phosphate followed by an osmotic shock with dimethyl sulphoxide (DMSO), polyethylene glycol (PEG) or glycerol did not prevent lactogenic hormones to induce casein synthesis. On the contrary and unexpectedly, casein synthesis was markedly stimulated by transfection. This amplification was obtained as well with DMSO, PEG and glycerol alone or in the presence of DEAE-dextran, calcium phosphate or DNA. None of these compounds induced casein synthesis in the absence of prolactin. A shock by DMSO also amplified the accumulation of beta-casein mRNA in the presence of prolactin. These results show for the first time that primary cultured mammary cells can be efficiently transfected and still keep their capacity to respond to lactogenic hormones. They also indicate that the short osmotic shocks conventionally used in transfection have a potent long-term stimulatory effect on casein gene expression, which is mediated through an unknown mechanism.