Development of basal lipolysis and fat cell size in the epididymal fat pad of normal rats

The normal development of adipose tissue lipolysis as measured by glycerol release was studied in epididymal fat pads of fed and fasted Sprague-Dawley rats between 15 and 128 days of age and correlated with changes in fat cell size. At 15 and 17 days of age, when fat cell size was small, glycerol release per cell was highest and decreased steadily to adult levels by 73 days of age. Between 85 and 128 days of age as fat cell size continued to increase, glycerol release per cell began to rise. Therefore, glycerol release per cell inversely correlated with fat cell size during early development and directly correlated with fat cell size after 73 days of age. The response to fasting was variable in the younger rats but was established by the third postnatal week. The possible early reciprocal and later complementary roles of lipolytic activity and lipoprotein lipase activity in the "setting" and regulation of fat cell size during postnatal adipose tissue development is discussed.