EFFECT OF STARVATION ON LIPOPROTEIN-LIPASE ACTIVITY IN DIFFERENT TISSUES DURING GESTATION IN THE RAT

This study was addressed to determine whether the tissue-specific LPL activity response to fasting differs between nonpregnant and pregnant rats over the course of pregnancy. Fed and 24-h fasted rats were studi ed at days 12, 15 or 20 of gestation and were compared to virgin contr ols. In fed rats at days 15 and 20 of gestation LPL activity decreased in lumbar adipose tissue and the heart and liver, and increased in ma mmary gland tissue. Fasting decreased LPL activity in lumbar adipose t issue in 12 day pregnant and virgin rats and in mammary gland tissue i n pregnant rats at 15 and 20 days of gestation and in virgin rats, whe reas it increased LPL activity in heart tissue in rats at day 15 and 2 0 and in liver at day 20 of gestation. Plasma triacylglycerols were hi gher in 20 day pregnant rats than in the other groups when fed and thi s difference was even more noticeable in the fasting condition where t he plasma beta-hydroxybutyrate level also reached the highest value in the 20 day pregnant rats. Since tissue LPL activity controls the hydr olysis and uptake of circulating triacylgylcerols, the present results indicate that in fed rats after the 15th day of gestation circulating triacylglycerols are preferentially taken up by the mammary gland ins tead of being taken up by adipose tissue and heart. However, after fas ting, circulating triacylglycerols are driven to the heart and liver i n the late pregnant rat, and become a major source for fatty acid oxid ation, an effect that seems to be specially evident in the liver of th e 20 day pregnant rat where there is an intense increase in LPL activi ty and the triacylglycerols become preferential substrates for ketone body production.