A PREADIPOSE 3T3 CELL VARIANT HIGHLY SENSITIVE TO ADIPOGENIC FACTORS AND TO HUMAN GROWTH-HORMONE

We describe a new Swiss 3T3 preadipose clone, 3T3-F442A/C4, which show s higher sensitivity to serum adipogenic factors and to human growth h ormone as compared to other 3T3 preadipose clones. The 3T3-F442A/C4 cl one exhibited several characteristics different from the parental 3T3- F442A cells, mainly a high extent of adipose conversion under culture conditions that are non-adipogenic for the parental cells. The 3T3-F44 2A/C4 cells are not committed to undergo adipose differentiation, sinc e they do not differentiate into adipocytes under serum-free or low-se rum culture conditions, unless adipogenic factors or growth hormone ar e added into the culture medium. The 3T3-F442A/C4 cells showed 1.5- to 3.6-fold higher sensitivity to serum adipogenic factors and 5- to 6-f old higher sensitivity to human growth hormone as compared to the 3T3- F442A cells. The 3T3-F442A/C4 variant clone also differed from the par ental clone by having a shorter population doubling time, an increased saturation density, and lower activity levels in some biochemical mar kers of adipose differentiation. On the other hand, the new variant cl one has a similar proportion of cells susceptible to become adipocytes , and a similar response to insulin as compared to the parental cells. Our results show that the 3T3-F442A/C4 cells represent a new 3T3 prea dipose clone that could be useful as a bioassay to evaluate growth hor mone activity, as well as to purify and characterize hormones, adipoge nic factors, and those compounds that affect mammalian adipogenesis.