Lipolysis induced by leptin in rat adipose tissue from different anatomical locations

The aim of the present work is to compare the lipolytic response of three fat depots (subcutaneous, epididymal and perirenal) to leptin under in vitro conditions in rats. Moreover an assessment of the potential differences between young and mature rats in terms of the response of these tissues to leptin is made. Adipocytes from 6- and 20-wk-old rats were isolated by collagenase digestion and incubated in vitro both in the absence and the presence of either leptin (10(-12)-10(-6) M) or isoproterenol (10(-6) M). Lipolysis was measured by the release of glycerol into the incubation medium over 2 hours of incubation. Adipocytes responded in a dose-dependent manner to leptin concentrations ranging from 10(-12) M to 10(-6) M. The lowest leptin concentration inducing a significant lipolytic effect was 10(-9) M in all tissues. No significant differences in the effect of the maximal concentration of leptin (10(-6) M) were observed among tissues for either age. The lipolytic effect of isoproterenol (10(-6) M) was significantly reduced in adipose tissues from mature rats; in contrast no significant differences in the effect of leptin (10(-6) M) were observed between young and mature rats. In summary, no anatomical-specific differences exist in the response of rat adipose tissue to lipid mobilization induced by leptin. Furthermore, this leptin action is not decreased in mature rats compared with young ones.