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A study of the various biological parameters of the blood in the genetically obese Zucker rat, the nonobese Zucker rat, and the Wistar rat has revealed great similarity between the two latter types of animals. On the other hand, in genetically obese Zucker rats as compared with the nonobese ones, (1) the blood mass per unit of weight was lower; (2) the level of nitrogenous degradation compounds was the same; (3) the lipase activity was lower; (4) the levels of substances for which liver plays a crucial role--all lipid and protein fractions, glucose, and the enzyme GPT--were higher; (5) the levels of Ca, Zn, Fe, Cu and Pi were high; (6) the blood and bone-marrow cells were unremarkable.

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.

The plasma concentrations of carnitine were determined in a group of 35 women and 35 men admitted to a clinic, and in another group of 18 women during their menstrual cycle. The values found for the women (45.1 +/- 2.6 nmol/ml of free carnitine and 59.1 +/- 2.8 nmol/ml of total carnitine) were not significantly different from the values obtained in men (respectively 42.4 +/- 1.7 and 55.5 +/- 1.9 nmol/ml). No direct relationship between the free or total carnitine concentrations and the concentrations of circulating lipids could be demonstrated. During the menstrual cycle the plasma concentrations of free and total carnitine remained unchanged. Intake of oral contraceptives caused an elevation in blood triacylglycerols and decreases in the levels of luteinizing hormone, follicle-stimulating hormone, and free and total carnitine.