Lipoprotein lipase activity in the liver of starved pregnant rats

We have previously described the appearance of lipoprotein lipase (LPL)-like activity in the liver of 24-hour-starved 21-day pregnant rat, but it is not known up to what point the appearance of this activity depends on the gestation stage and/or the length of the starvation period. We found that 24 h of starvation resulted in the appearance of LPL-like activity in the liver of 21-day-pregnant but not in 17-day- or nonpregnant rats. This appearance was found only after 24 h but not after 48 or 72 h of starvation. We demonstrate that this activity actually corresponds to LPL, since it is inhibited by either 1.5 M NaCl or 1.5 mg/ml protamine sulfate, is serum-dependent, and could be separated from hepatic lipase activity by using heparin-Sepharose affinity chromatography. The possible relationship between the appearance of LPL activity in the liver and the enhanced metabolic response to starvation in pregnant rats at term is discussed. It is suggested that the presence of this enzyme in the liver would allow the direct uptake by the liver of circulating triacylglycerols.