Influence of norethindrone on lipid metabolism and cholelithiasis in rabbits.

Rabbits were fed a purified ration containing 15% lard and were killed and examined at 0, 4, 8, 12, and 16 weeks. One group (group II) was given (treated) norethindrone in the ration (10 mg/kg of ration). There were no treatment effects noted on hepatic weight, percentages of dry matter and ether extract in liver, and hepatic cholesterol concentrations; however, there were some changes in the hepatic fatty acid percentages at some observation times. The occurrence and severity of cholelithiasis were not influenced by the treatment, but gallstone formation was pronounced in the 2 groups (ration alone, ration with added norethindrone) by the 4th weeks. The thoracic aorta did not reveal treatment effects as to weight and percentages of dry matter and ether extract, but the aortic cholesterol concentration was greater in the nontreated group than in the group fed the ration with the added norethindrone. Increased thoracic aortic weights were noted in both groups by the 4th week. Examinations and analyses of the adipose deposits forming the kidney pads did not reveal influences of time or treatment.