Abstract
1. 1. The effect of pregnancy and lactation on lipoprotein lipase activity in adipose and mammary tissues and on plasma triglyceride concentration were studied in the rat. 2. 2. Plasma triglyceride concentration, 0.9 mM in control rats, increased 3-fold between the 12th and 20th days of pregnancy to a peak of 3.3 mM, and then decreased 50% during the next 2 days. It increased again at parturition, on the 22nd–23rd days of pregnancy, to 3.0 mM, and then fell sharply and remained below 1.0 mM throughout lactation. 3. 3. Lipoprotein lipase activity in parametrial adipose tissue, 12 units/g in control rats, increased 2-fold between the 9th and 12th days of pregnancy and then decreased slightly during the next 7 days, (1 unit of lipoprotein lipase activity = 1 μmole of triglyceride hydrolyzed per h.) It decreased on the 20th day to 5 units/g, reached 2 units/g at parturition, and remained below 2 units/g throughout lactation. 4. 4. Lipoprotein lipase activity in the inguinal-abdominal mammary glands increased very slowly during the first 20 days of pregnancy, from 0.9 units/g to 7 units/g. It then increased the next day to 21 units/g, decreased sharply at parturition to 6 units/g, and increased after parturition to more than 40 units/g. Lipoprotein lipase activity in mammary gland remained high as long as the mother suckled. 5. 5. Nonsuckling for 9 or more h decreased mammary gland lipoprotein lipase activity to near zero and increased plasma triglyceride concentration to 3 mM. Nonsuckling also increased lipoprotein lipase activity in adipose tissue. 6. 6. Ligation of the lactiferous ducts of the inguinal-abdominal glands on one side markedly reduced the lipoprotein lipase activity in these glands but not that in the contralateral, suckled glands. 7. 7. Plasma triglyceride concentration was inversely related to the lipoprotein lipase activity in mammary tissue during the last 2 days of pregnancy and throughout lactation. 8. 8. It is suggested that the changes in lipoprotein lipase activity of adipose and mammary tissues that occur during late pregnancy and lactation serve to divert dietary lipid from storage in adipose tissue to mammary glands for milk formation.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism
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