Acceleration by triiodothyronine of adipose conversion of rat preadipocytes from two adipose localizations

Since we have previously reported that hyperthyroidism induces adipose tissue hyperplasia in the young rat, the effect of thyroid hormones on growth and differentiation of preadipocytes from retroperitoneal (RPAT) and epididymal (EAT) adipose tissue was studied in a primary culture system which allows a precocious cell differentiation. In this culture system, preadipocytes from RPAT exhibited a greater potentially to differentiate than cells from EAT. Chronic exposure to triiodothyronine (T3) induced an acceleration of the differentiating process as shown by a transient increase of the number of differentiated cells without alteration of cell multiplication. This effect was more important in cultures of cells from RPAT than from EAT. T3 was ineffective on lipoprotein-lipase activity but induced a stimulation of the esterification pathway which was durable and could likely be related to an increased lipid turn-over. T3 induced also a stimulation of fatty acid biosynthesis, only on the first stages of morphological differentiation which suggests that this effect could be specifically in relation with the stimulation of adipose conversion.