Maintenance of normal rat mammary epithelial cells by insulin and insulin-like growth factor 1.
Normal rat mammary epithelial cells were cultured within a rat tail collagen gel matrix formed under improved conditions for controlling pH and osmolarity. Under these conditions, growth can be maintained for up to 3 weeks with a 10- to 15-fold increase in cell number. The cells grow in response to prolactin, progesterone, epidermal growth factor, and cholera toxin, in a medium of DME: Ham's F12 supplemented with BSA and insulin at 10 micrograms/ml. When the insulin concentration was reduced to more physiological levels (10 ng/ml) the cells did not grow. However, at these more physiological concentrations it could be shown that insulin had a concentration-dependent effect on the maintenance of the cells with an optimum concentration around 25 ng/ml. The cells could be maintained in hormone-supplemented medium with low levels of insulin in a quiescent state for up to 14 days. The high levels of insulin needed for optimal growth could be replaced by insulin-like growth factor 1 (IGF-1) at much lower concentrations (25-50 ng/ml). The superphysiological level of insulin required for optimum growth is probably due to its acting weakly through an IGF-1-mediated growth-promoting mechanism. Insulin's effect on cell maintenance occurs at physiological levels and may better reflect its role in mammary cell growth.
Deeks
S
S
Cancer Research Laboratory, University of California, Berkeley 94720.
Richards
J
J
Nandi
S
S
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology; D003094:Collagen; D003470:Culture Media; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004847:Epithelial Cells; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006854:Hydrocortisone / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008321:Mammary Glands, Animal / Q000166:cytology*; D009994:Osmolar Concentration; D011374:Progesterone / Q000494:pharmacology; D011388:Prolactin / Q000494:pharmacology; D051381:Rats; D011917:Rats, Inbred Lew; D013002:Somatomedins / Q000494:pharmacology*
D003470:Culture Media; D007328:Insulin; D013002:Somatomedins; D011374:Progesterone; D004958:Estradiol; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D003094:Collagen; D002772:Cholera Toxin; D006854:Hydrocortisone