Lipoprotein lipase and uptake of chylomicron triglyceride by skeletal muscle of rats

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Abstract
Uptake of chylomicron triglyceride and lipoprotein lipase was studied in red and white skeletal muscles, heart, and adipose tissue of rats. Retention of triglyceride fatty acids 10 min after injection was 1.6%/g in heart and adipose tissue, 0.2-0.4%/g in red (soleus and diaphragm) muscles, and 0.1%/g in white (psoas minor) muscles of fed rats. Fasting (24 h) increased retention 2- to 4-fold in red skeletal muscles and heart, had no effect in white muscles, and decreased retention > 75% in adipose tissue. Lipoprotein lipase activity in fed rats was lowest in white muscles and in certain red (posterior belly of digastric and medial head of triceps brachii) muscles, intermediate in soleus and diaphragm muscles and adipose tissue, and highest in heart. Fasting doubled lipoprotein lipase activity in all red skeletal muscles and heart, had no effect in white muscles, and decreased activity 60% in adipose tissue. Triglyceride uptake is apparently related to lipoprotein lipase activity in skeletal muscle and the changes in enzyme activity during fasting divert blood triglyceride to red skeletal muscles.