LIPID-CONTENT AND LIPOPROTEIN-LIPASE ACTIVITY IN SKELETAL-MUSCLE OF LACTATING AND WEANED RATS

The aim of the investigation was to study the changes in lipid content and lipoprotein lipase (LPL) activity of skeletal muscle of lactating and weaned rats, in order to gain insight on the role of skeletal mus cle in the metabolism of triacylglycerols not used by the mammary glan d after weaning. Sprague-Dawley rats fed ad libitum were killed 0, 8, 12, and 24 h after litter separation on the 14th day of lactation. Ele ctron microscopy, as well as determinations of the total fat and phosp holipid content were performed on muscles of the right hind limb. Lipo protein lipase activity was determined in extracts of acetone powder o f skeletal muscle, mammary gland, and adipose tissue using dibutyryl f luorescine as substrate. Fat droplets were identified in the muscle in terfiber spaces of weaning rats. Muscle total fat and phospholipids we re higher in weaned than in lactating rats. After litter separation, l ipoprotein lipase activity increased significantly in muscle and in ad ipose tissue (fourfold), while activity in the mammary gland decreased . The increased muscle lipoprotein lipase activity in the weaned rats seems to be associated with the higher content of fat and with the pre sence of fat droplets.