Adipose tissue lipolytic rate in genetically obese and lean swine

In vitro lipolytic rate was determined in adipose tissue from genetically obese and lean pigs. There were about 20 pigs/genetic strain at 25 and 80 kg and 10 pigs/strain at 50 kg body weight. When expressed on a cellular basis, the in vitro adipose tissue basal (no exogenous hormone) lipolytic rate was similar in obese and lean pigs at 25 and 50 kg body weight. At 80 kg body weight the basal rate was greater in obese than in lean pigs. The in vitro adipose tissue epinephrine-stimulated lipolytic rate expressed on a cell basis was greater at 25 kg, was similar at 50 kg body weight and tended (P less than or equal to .1) to be greater at 80 kg in obese compared with lean pigs. The in vitro sensitivity of lipolysis to epinephrine was slightly greater in lean compared with obese pigs. The data obtained in vitro indicate that obese pigs do not have low adipose tissue lipolytic rates compared with lean pigs. Consequently, adipose tissue lipolysis does not appear to be a major metabolic factor leading to the excessive fat accretion in these obese pigs.