UBC Theses and Dissertations
The effect of litter size on the developmental pattern of cholesterol synthesis in intestinal and white adipose tissue of neonatal rats Kroeger, Steven Hugh
This study was performed to determine the rates of in vitro cholesterol synthesis, as measured by ³H incorporation into cholesterol, in gluteal white adipose tissue and the intestine of infant rats during the early postnatal period. The reason for studying these parameters was to hopefully further elucidate the cause of the differences in blood cholesterol levels between rats raised in different litter sizes. Rats were raised in small (4/dam), medium (8/dam) and large (14/dam) litters. The rate of cholesterol synthesis in the proximal and distal region of the small intestine decreased from birth to a low 14 days later and then increased again by day 21. The rate of the decreases in cholesterol synthesis, from birth to the low on day 14, varied amongst the three litter sizes; the rate of synthesis in both regions of the intestine on day 7 was lowest in the larger litter, and was not significantly different from the values seen on day 14. Previous work has shown that plasma cholesterol levels were low in rats from large litters on day 7, thus in the early postnatal period low rates of intestinal cholesterol synthesis correlate with low plasma cholesterol values. After weaning, on day 21, the rate of synthesis in distal intestine was higher than that of proximal intestine in the medium and small litters, whereas the opposite was found in the larger litter. Cholesterol synthesis in gluteal white adipose tissue remained at a very low rate up to 21 days in the small and medium sized litters. In contrast, the rate of synthesis increased continuously in the large litter to nearly threefold the rate of that in the other two litter sizes on day 21. This study has shown that the rates of cholesterol synthesis in intestinal and adipose tissue can be altered during the early postnatal period by raising the rats in different litter sizes. Also, the pattern of development in the rates of cholesterol synthesis as measured by ³H incorporation into cholesterol are in general agreement with results reported for the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase for this same period in development.
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