Increased DNA synthesis in adipocytes and capillary endothelium in rat adipose tissue during overfeeding.

Adult male rats were subjected to overfeeding with a high-fat, high-sugar diet for 3 and 7 days resulting in a moderate expansion of adipose tissue depots by an increase in fat-cell size. Seventeen hours and 7 days after injection of a pulse of labelled thymidine, specific activity of DNA was examined in different cellular fractions obtained from the epididymal and perirenal adipose tissues after collagenase liberation and separation procedures. A slow increase of formation of new adipocytes occurred after 3 and 7 days of overfeeding, most pronounced in cells from perirenal adipose tissue. Capillary endothelium and cells in the stromal fraction showed a rapid synthesis and turn-over. Overfeeding induced an increased formation of new capillary endothelial cells after 7 days of overfeeding, again most pronounced in perirenal cells. It was concluded that new fat cells are formed at a slow rate early during overfeeding. Capillary endothelium in adipose tissue has a high rate of turnover, and its synthesis is increased further by overfeeding. New adipocytes precede, and possibly stimulate, the formation of new capillaries. Formation of new cells in the remaining stromal-vascular cells is probably occurring at different rates among different types of cells.