Uptake of [alpha ]-tocopherol by the mammary gland but not by white adipose tissue is dependent on lipoprotein lipase activity around parturition and during lactation in the rat

Abstract

This study was undertaken to test the potential role of changes in lipoprotein lipase (LPL) activity in the mammary gland and adipose tissue around parturition and lactation on the uptake of [alpha ]-tocopherol in the rat. Plasma levels of [alpha ]-tocopherol and triglycerides were higher in 20-day pregnant rats than in virgin rats, whereas its concentration was higher in the mammary gland of the former, and no differences were detected in adipose tissue between the groups. After an oral [alpha ]-tocopherol and triglyceride load, both appeared in plasma faster in pregnant rats than in virgin rats, the change being even faster for [alpha ]-tocopherol than for triglycerides. After 24 hours, both [alpha ]-tocopherol and triglycerides in d [lt ] 1.006 lipoproteins were higher in pregnant rats than in virgin rats, LPL activity was higher in the mammary gland, and lower in adipose tissue in the former, whereas [alpha ]-tocopherol concentration also appeared higher in the mammary gland of pregnant rats, and no differences were detected between the groups in adipose tissue. At day 13 of lactation, an oral load of [alpha ]-tocopherol and triglycerides caused a higher increase of plasma [alpha ]-tocopherol levels than triglycerides, and this effect decreased when rats had their litter removed 48 hours before analysis. In these litter-removed rats, the appearance of [alpha ]-tocopherol and triglycerides in plasma was higher in d [lt ] 1.006 lipoproteins than in lactating rats. Also, both LPL activity and [alpha ]-tocopherol concentration in the mammary gland plus milk was lower in litter-removed rats than in the lactating rats, whereas LPL in adipose tissue was higher in the former, although no difference in [alpha ]-tocopherol was found. Thus, data are consistent with the role of LPL activity in the mammary gland modulating the uptake of [alpha ]-tocopherol during pregnancy and lactation, although this is not true in adipose tissue.