12-O-tetradecanoylphorbol-13-acetate (TPA) stimulates the adipose conversion of piglet preadipocytes in primary culture.

The effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) were analyzed on the proliferation and differentiation of cultured porcine preadipocytes. In both chemically-defined and serum-containing media, short term treatment (2 days), either during the growth phase or from confluence, significantly enhanced cell proliferation, as assessed by tritiated thymidine incorporation and protein content assay. Addition of TPA during the growth phase in serum-free medium had no effect on lipoprotein lipase (LPL), glycerol 3-phosphate dehydrogenase (GPDH) and malic enzyme (ME) activities after 14 days of culture. By contrast, similar treatments in serum-containing medium significantly increased all these enzyme activities. Addition of TPA from confluence in both media stimulated LPL activity on day 14 as well as ME activity on day 17. These results were confirmed by morphologic studies. In conclusion, this study demonstrates that a short stimulation of the protein kinase C pathway can enhance the differentiation of porcine preadipocytes. Such a positive effect is however dependent on the time of TPA addition as well as the culture conditions, indicating a complex regulation of the protein kinase C pathway in this cell type.