Response of lipogenic enzymes to intensity and duration of overfeeding in the adult Japanese quail (Coturnix coturnix japonica).

I . Adult male Japanese quail (Coturnix Coturnix Japonica) were overfed at different intensities during varying periods: (I) by gradually increasing the daily amount of food up to twice the control level in a period of 1 1 d and keeping this level constant during the subsequent 12 d period (prolonged overfeeding); ( 2 ) by gradually increasing the daily amount of food up to approximately twice the control level in a period of 6 d (short, low-intensity overfeeding; SL); (3) by gradually increasing the daily amount of food up to approximately 25-fold the control level in a period of 7 d (short, high-intensity overfeeding; SH). 2. The activities of acetyl-CoA carboxylase (EC 6.4.1.2; CBX), fatty acid synthetase (FAS), ATP citrate lyase (EC 4 . I . 3 . 8 ; CCE) and malate dehydrogenase (decarboxylating) (NADP) (EC I . I . I .40; ME) were determined in adipose tissue (AT) and liver of the overfed and ad fibfed chicks. Size and fat content of carcass, AT and liver were also determined in order to evaluate the extent of obesity. 3. The weight of carcass, lean body mass, liver and AT and the extent of fat deposition increased with the total amount of food consumed. Obesity was particularly pronounced in quail after prolonged overfeeding. 4. Lipogenic enzymes in liver were much more active than those of AT. The specific activities of CBX, FAS and CCE in liver and AT in overfed Japanese quail increased consistently in the SL and SH groups only and the increase was related to the level of food intake in these groups. ME was the only enzyme whose specific activity increased in all overfed groups. Total AT enzyme activities were increased most strongly after prolonged overfeeding because of the pronounced tissue enlargement in that treatment. But in liver, where tissue enlargement was less and differences in size due to the three overfeeding treatments were less marked, total activities depended mainly on the enhancement of specific activities. 5 . The results lead to the conclusion that the increase in hepatic lipogenic enzymes roughly reflects the current food intake and may thus be considered to represent the primary adaptation in the overfed Japanese quail. Secondary adaptation, involving tissue enlargement, occurs principally in AT of Japanese quail after prolonged overfeeding, in which situation AT contributes significantly to total lipogenic activity.