1. Investigación

From parturition, lactating Wistar rats were given 20% ethanol in drinking water and solid diet ad lihitum (ET group) or were pair-fed to the ET group (PF group) or were given water and solid diet ad lihitum (control group, C). Animals were studied on day 12 of lactation and/or treatment, when dams were separated from their litters and 2-4 hours latter they were i.p. injected with oxytocin for milk collection under anaesthesia. Maternal food intake, weight gain and pup's body weight were lower in ET than in C rats. When compared to C rats, milk of ET dams had a decreased proportion of C14:0 and C22:6 n-3 fatty acids while an increase in C18:0, C16:1 and C18:1 n-9 was detected, whereas when compared to PF it had higher CS:0, Cl0:0, C18:0, C18:1 n-9, C18:2 n-6 and lower C20:5 n-3 and C22:6 n-3. Body weight was lower in pups from ET than in those from C or PF, and whereas brain weight and brain lipid content was lower in ET and PF pups than in C, total phospholipid (PL) brain content was similar among the groups. The ratio of C20:3 n-9 to C20:4 n-6 in brain PL was higher in ET pups than in either C or PF, indicating an essential fatty acid deficiency in the formers. Ethanol treatment also decreased the proportional amount of C18:2 n-6, C18:3 n-3, C20:4 n-6, C20:5 n-3 and C22:6 n-3 in brain PL as compared to C, whereas from these fatty acids only C18:3 n-3, C20:5 n-3 and C22:6 n-3 were decreased in PF. On the other hand, the proportion of C22:6 n-3 was significantly lower in the pups of ET group than in PF animals. Present results show that maternal intake of ethanol during lactation in the rat modifies milk lipid composition and that these effects are not caused by the undemutrition condition of the animals. These effects alter fatty acid composition of brain PL in pups, and such effect may contribute to its abnormal development.

A technique previously used to study placental transfer in pregnant rats, consisting of labeled tracer infusion through the left uterine artery, was employed to determine the utilization oflipogenic substrates by periuterine adipose tissue in the fed and 48-hr starved female virgin rat. After 20 min infusion with either D[U- 14C]glucose, L-[U- 14C]alanine, [U14C]glycerol or L-[U- 14C]lactate, the radioactivity appearing in periuterine adipose tissue 14C-labeled lipids from the left side was always higher than that appearing in tissue from the right side. Negligible radioactivity was detected in the tissue from either side when the infusion was done with non-metabolizable derivatives such as L-[1- 14C]glucose or [1- 14C]a-aminoisobutyric acid. Simultaneous infusion ofL-[U- 14C]alanine and an alanine transaminase inhibitor (aminooxyacetic acid) into the left uterine artery completely blocked the conversion of the alanine into periuterine adipose tissue 14C-labeled lipids. The utilization of the infused substrate for fatty acids and glyceride-glycerol synthesis by the tissue was quantified by taking into account the infused radioactivity, the difference in the amount of 14C-labeled lipids appearing in periuterine adipose tissue on the left and the right sides, the arterial plasma concentration of the studied metabolite, and the uterine horn blood flow. In fed animals, the highest fatty acid synthesis was found with lactate, followed by glucose, alanine, and glycerol. This process was intensely decreased with all the substrates in 48-hr starved rats. In fed animals the synthesis of glyceride-glycerol was highest with glucose followed by lactate, alanine, and glycerol. In the starved rats it did not change with lactate and decreased with both alanine and glycerol. Besides validation of the technique for the study of periuterine adipose tissue metabolism in situ, results show the efficient utilization of lactate as lipogenic and of glucose as glycerogenic substrates. On the basis of the known capacity of adipose tissue to synthesize alanine from other amino acids, we propose that in the fed state this tissue may use different amino acids for lipogenesis. The negligible use of glycerol by periuterine adipose tissue in situ contrasts to its known utilization in vitro indicating that, whereas glycerokinase activity in the tissue may have a role in the re-utilization of glycerol released into the tissue, it does not contribute to the use of circulating glycerol.

Lipidic components, as well as fatty acid composition and vitamin E content were determined in colostrum (days 3-5 of postpartum) and mature milk (day 21) in 8 women from Murcia (Spain). Triglycerides concentration was higher and cholesterol and estcrificd cholesterol ,vcre lower in mature milk than in colostrum, whereas phospholipid content was similar. These differences indicate that the diameter oi milk fat globules increases in mature milk. The percentage oi medium-chain fatty acids (12:0 and 14:0) increased in mature milk as compared to colostrum, reflecting de no·vo svnthesis of fatty acids. With the only exception of stcaric acid which was lower in mature milk than in colostrum, the remaining long-chain fatty acids was similar. The proportion of both linoleic (18:2) and eicosapcntaenoic (20:5) acids found in mature milk and colostrum is higher than in studies from other countries and mav reflect the intake of high proportions of polyunsaturated fat from vegetable oils and fish in the studied women. Both vitamin E content and vitamin E/linoleic acid ratio in mature milk arc lower than in colostrum, evidencing the efficient mechanism of mammary gland vitamin E uptake around parturition.