Rapid changes in rat heart lipoprotein lipase activity after feeding carbohydrate.
The effect of feeding various carbohydrates on the activity of lipoprotein lipase (LPL) released by heparin from perfused rat heart was investigated. Animals fasted for 8 to 12 hours were given a single 3-ml dose of 60% (w/v) glucose, sucrose or fructose solution or 3 ml water by intubation. After various time intervals, the hearts were removed and perfused with Krebs-Ringer bicarbonate buffer containing 1 unit heparin/ml. The perfusate was then assayed for LPL activity. From 35 to 80 minutes after feeding the LPL activity released by heparin from hearts of the glucose fed animals decreased 85% compared to the LPL activity released from hearts of the control group fed water. A similar decline in lipase activity was seen in the sucrose-fed group. In contrast to the glucose and sucrose data, fructose feeding produced no change in the heparin-releasable LPL activity compared with the control animals fed water. The LPL activity remaining in the heart tissue after perfusion with heparin was not significantly different in the experimental and control groups. The capacity of the hearts to hydrolyze 14C-labeled chylomicrons following glucose or sucrose feeding was also reduced by 70 to 85%.