The influence of early nutrition on the serum cholesterol of the adult rat.

In two experiments, young rats were preconditioned with dietary cholesterol by: 1) nursing from dams with a high cholesterol milk or, 2) receiving 10 mg cholesterol dissolved in 0.5 ml of corn oil daily from 6 to 30 days of age. When rats preconditioned with dietary cholesterol in early life were fed stock diet supplemented with 10% lard and 0.5% cholesterol ("cholesterol challenge diet") there was no protection against dietary induced hypercholesterolemia in adult life. In a third experiment, two groups of newborn rats were intubated with: 1) a cholesterol free formula, 2) the cholesterol free formula plus 50 mg% cholesterol. A third group of pups suckled normally. After weaning all pups were fed a stock diet supplemented with 10% lard and 0.5% cholesterol for 1 month. There was no difference in the serum cholesterol in either group of artificially reared rats after the "cholesterol challenge" (106 +/- 6 mg/100 ml). Suckled rats, however, had a lower serum cholesterol after the "cholesterol challenge" (75 +/- 2 mg/100 ml). All experiments conducted refute the hypothesis that early exposure to dietary cholesterol protects against dietary induced hypercholesterolemia in adult life. It appears, however, that cholesterol metabolic systems are affected in early life because of the decreased ability of artificially reared rats to handle a "cholesterol challenge." Possible factors include a component of the dam's milk, growth and development, and the psychological and emotional stress of the artificial rearing process.