Serum lipids in 8- to 35-day-old Zucker rats

The serum concentrations of triacylglycerols, cholesterol, and phospholipids were measured in 8- to 35-day-old Zucker rats. The animals were killed at 35 days of age. and their phenotype is determined on the basis of the weight of their inguinal subcutaneous fat pads. The serum lipid concentrations in all the rats increased from the 8th day of life, reaching a maximum at day 17 to 21. Weaning produced a large decrease in the concentrations of all three types of lipids. In the obese rats, the serum concentration of triacylglycerols was significantly raised from day 35 of life, that of cholesterol from day 21, and that of phospholipids from as early as day 8. At this age this latter concentration nevertheless cannot be used as a factor for detecting the obese phenotype.