1. Investigación

La dieta rica en sacarosa (DRS) no modifica el peso corporal de la rata gestante ni de sus fetos. La práctica de un ejercicio aerobio moderado tampoco afecta a estos parámetros con independencia del tipo de dieta que ingieran o de su estado fisiológico. La respuesta metabólica a la DRS es diferente según el metabolito estudiado, así la hipertrigliceridemia es similar en ratas vírgenes y preñad3s, aunque en estas últimas el efecto de la DRS se suma al aumento de triglicéridos característico de la gestación. Los niveles de ácidos grasos libres no se modifican ni en vírgenes ni en preñadas como consecuencia de la DRS. En lo relativo a la glucemia e insulinemia existe una respuesta diferencial a la DRS dependiendo de que los animales estén o no preñados. Finalmente, la práctica de ejercicio reduce considerablemente la insulina en las ratas gestantes alimentadas con DRS o con la DC.

A method for vitamin E (a-tocopherol) measurement in rat adipose tissue and mammary gland has been developed and validated. Tissues were homogenized in ethanol–water (1:1) and extracted with n-hexane. Vitamin K was used as internal 1 standard. Separation was performed by HPLC with methanol–water (96.5:3.5) as eluent in a Nucleosil C column 18 (1530.46 cm) at 408C. Detection was by fluorescence with excitation at 295 nm and emission at 350 nm for vitamin E and at 330 and 440 nm for vitamin K . Standards and tissue extracts were checked for linearity giving correlation coefficients over 1 0.99 in a range of concentrations from 0.56 to 4.51 nmol/g in adipose tissue and from 2.18 to 17.4 nmol/g in mammary gland tissue. Intra-assay precision (R.S.D.) varied between 3 and 4%, whereas inter-assay precision was between 8 and 9%. Recoveries ranged between 9563% and 98611% for the two tissues, respectively. Vitamin E was measured in rats that had previously received one oral dose of this vitamin. Whereas vitamin E content in adipose tissue did not differ between late-pregnant and virgin rats, it was significantly higher in mammary gland of pregnant rats, and this difference could be related to the enhanced lipoprotein lipase activity in this group.

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 -tocopherol in the rat. Plasma levels of -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 -tocopherol and triglyceride load, both appeared in plasma faster in pregnant rats than in virgin rats, the change being even faster for -tocopherol than for triglycerides. After 24 hours, both -tocopherol and triglycerides in d < 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 -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 -tocopherol and triglycerides caused a higher increase of plasma -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 -tocopherol and triglycerides in plasma was higher in d < 1.006 lipoproteins than in lactating rats. Also, both LPL activity and -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 -tocopherol was found. Thus, data are consistent with the role of LPL activity in the mammary gland modulating the uptake of -tocopherol during pregnancy and lactation, although this is not true in adipose tissue.