Nitrogen metabolism in o,p′-DDT-fed rats

Urea synthesis from 5 mm NH₄Cl plus 10 mm ornithine was decreased in isolated hepatocytes from rats fed 1000 ppm o,p′-DDT for 2 weeks and starved for 48 hr. DDT feeding had no effect on urea synthesis from 10 mm alanine, serine, or threonine in the presence of 10 mm ornithine. When rats were not starved prior to hepatocyte isolation, rates of urea synthesis from 10 mm NH₄Cl plus 10 mm ornithine were similar in hepatocytes from control and DDT-fed rats. In vivo, DDT-fed and subsequently starved rats had the same survival rate as starved controls after injection of 5 mmol NH₄Cl/kg body weight. Plasma urea levels were also similar. A feeding study demonstrated that rats fed a 90% casein diet supplemented with 1000 ppm o,p′-DDT gained weight at the same rate as rats fed only the 90% casein diet. Hepatocytes were then isolated from these rats, and it was found that rats fed the 90% casein diet plus DDT exhibited decreased rates of urea synthesis from 10 mm NH₄Cl plus 10 mm ornithine. These data show that DDT feeding resulted in a decreased capacity for urea synthesis from NH₄Cl in hepatocytes from starved and high-protein-fed rats. This reduced capacity did not appear to decrease in vivo ammonia detoxification under the conditions studied.