The effects of various mammalian sera on attachment efficiency and thymidine incorporation in primary cultures of mouse mammary epithelial cells.

Mammary epithelial cells from 16- to 17-day pregnant BALB/c mice were cultured in various mammalian sera to determine the kind of serum which stimulates optimal attachment efficiency and thymidine incorporation. Of those sera tested, horse, bovine, lamb, goat and fetal bovine provided the highest attachment efficiency, whereas rat, mouse and human gave the lowest. Rabbit serum stimulated the highest thymidine incorporation into TCA-insoluble material with goat and rat providing the lowest. These results suggest that sera which provide the highest attachment efficiency for primary cultures are not the best stimulants of DNA synthesis and show that an inverse relationship exists between cell attachment and thymidine incorporation for any given type of mammalian serum.