Characteristics of the rat adipoblast during differentiation in culture.

In the present study, stromal vascular cells were obtained from the inguinal fat pad of 3-day-old rats and layered on a continuous density gradient (Percoll). After centrifugation, it was possible to collect three homogeneous cell populations of different densities and to grow them separately in primary culture. Upon reaching a confluent state two of them particularly (the lighter fractions) converted to adipocytes with a high frequency (90 per cent) in the presence of physiological concentration of insulin (10(-8) M). During the adipose conversion insulin markedly enhanced the activities of lipogenic enzymes. When VLDL (350 micrograms lipids/ml) and heparin (10 IU/ml) were added to the medium, this effect was not potentiated. However VLDL and heparin in presence of insulin increased the triacylglycerol content of the differentiated cells. The heavier fraction did not undergo adipose conversion to the same extent as the lighter ones. It was concluded that the high ability of these precursor cells to convert to adipocytes and their response to low concentration of insulin could be related to the early development stage of the tissue.