Biomedical subjects

X Remesar

Publications and source records attributed to X Remesar.

At least 127 records · Page 7Linked to original sources

PubMed1989

Altered ultrastructure of lactating rat mammary epithelial cells induced by chronic ethanol ingestion.

The ethanol and acetaldehyde uptake by the lactating rat mammary gland as well as their effects on this gland at the ultrastructural level have been studied. The extraction of acetaldehyde was greater than that of ethanol both after chronic and acute ethanol treatment. Chronic ethanol administration resulted in a loss of the mammary cell polarization, in a reduction of the Golgi dictyosomal elements and in several abnormalities at the level of casein maturation and secretion, whereas lipid synthesis and secretion did not seem to be affected. Normal spherical casein micelles took on a filament-like structure and casein vesicles appeared fused together forming macrovesicles. All these alterations were specific of ethanol and/or acetaldehyde action and were not due to the associated malnutrition, as deduced from the lack of visible effects in the nutritional control group.

Acetaldehyde↗

PubMed1989

Na+-dependent alanine transport in plasma membrane vesicles from late-pregnant rat livers.

Liver plasma membrane vesicles retaining Na+-dependent L-alanine transport were purified from either virgin or 21-d pregnant rats. Kinetic analysis of L-alanine uptake data revealed that vesicles from pregnant rats show a slight increase in Vmax without significantly affecting Km. Plasma membrane marker recoveries were used to calculate alanine utilization indexes. These data showed that the overall liver capacity to take up alanine was increased 2-fold in late pregnant rats. When considering utilization indexes in the physiologic range of L-alanine concentrations in blood (0.1-2 mM), we found a highly significant enhancement of the liver capacity to take up this amino acid. It is concluded that, at late pregnancy, when amino acid requirements by the fetus are high, amino acid disposal by the maternal liver is not limited by a low transport capacity; thus, other mechanisms should be contributing to the nitrogen sparing at late pregnancy.

Alanine↗

PubMed1988

Glutamine as a major nitrogen carrier to the liver in suckling rat pups.

We measured the amino acid concentrations in the afferent and efferent vessels of the liver in anaesthetized fed adult rats and in fed suckling rat pups. A much higher content of glutamine in the portal vein and the aorta than in hepatic veins suggests that this amino acid is actively taken up by the liver of fed suckling rat pups, conversely to what is found in adult rats. In an attempt to characterize further the mechanism(s) contributing to this enhanced glutamine uptake, we monitored the time course of 1 mM-glutamine transport into plasma-membrane vesicles purified from the livers of either adult or suckling rats. The concentrative Na+-dependent uptake of glutamine was lower in those vesicles obtained from pups than in those obtained from adult rats. Glutaminase and glutamine synthetase activities in livers from both experimental groups were also measured. Glutaminase and glutamine synthetase activities in suckling rats were about 3-fold higher and 2-fold lower respectively than those in adult rats. It is concluded that glutamine is a main nitrogen carrier to the liver in fed suckling rats. A high availability of this amino acid and an enzyme imbalance between glutamine-synthesizing and -degrading activities may account for the net uptake found in vivo.

Amino Acids↗

PubMed1988

Carrier-mediated uptake of L-(+)-lactate in plasma membrane vesicles from rat liver.

Plasma membrane vesicles from rat liver transported L-lactate into the inner vesicular space. Kinetic analysis of L-lactate uptake gave a Km value of approx. 2.9 mM. Selective inhibition was found in a similar pattern to that described for the hepatic lactate carrier. L-Lactate transport was enhanced when a pH gradient was created across the plasma membrane. Vesicles obtained from fasted rats showed a higher uptake of L-lactate than those from fed rats, when incubated with physiological concentrations of L-lactate.

Alanine↗

PubMed1988

Alanine turnover rate and its hepatic metabolism are increased in midpregnant rat.

At mid pregnancy (12th day) fed rats exhibit a drop of blood alanine level when the weight of the fetoplacental unit is still negligible. A primed infusion A-V method was used to measure alanine kinetics in fed midpregnant rats and virgin controls, using L-[2,3-3H]alanine as a tracer. Alanine turnover and metabolic clearance rates were higher on day 12 than in virgin controls. The increase in alanine turnover rate was accounted for by an increase in alanine degradation. Since the liver is the main site of alanine degradation, alanine uptake was studied in isolated hepatocytes. Hepatocytes isolated from midpregnant rats utilized 50% more alanine than those from virgin controls. This increase was mainly due to metabolism rather than incorporation into proteins. In conclusion, the alanine turnover rate and its hepatic metabolism are increased in fed midpregnant rats, resulting in the decrease in blood alanine.

Alanine↗

PubMed1987

Hepatic uptake of amino acids in late-pregnant rats. Effect of food deprivation.

Hepatic availability, uptake and fractional extraction of amino acids were estimated in anaesthetized 21-day-pregnant and age-matched virgin rats, either fed or after 24 h starvation. Amino acid availability was unaltered in fed pregnant rats as compared with fed virgin controls. However, the hepatic uptake of these compounds was higher in the former than in the latter. These adaptations were mediated by an increase in the hepatic capability to take up amino acids in late-pregnant rats, as reflected by the changes found for the fractional extraction rates. The decrease in amino acid availability found after starvation was more pronounced in pregnant than in virgin rats. Nevertheless, the hepatic uptake was similar in both groups. These results indicate that amino acids are not limiting for ureagenesis during late pregnancy, strongly suggesting that the mechanism(s) which modulate urea synthesis may be intracellular in origin.

Amino Acids↗

PubMed1987

Hepatic uptake of amino acids at mid-lactation in the rat.

Hepatic availability and uptake of amino acids were measured in fed virgin and 15-day-lactating rats. Lactation did not induce any change in total amino acid availability (expressed per 100 g body wt.). Virgin rats showed a nil hepatic balance, and lactation induced a high net uptake. The high drainage of amino acids by mammary gland does not affect hepatic availability.

Amino Acids↗

PubMed1987

Effects of chronic ethanol treatment on amino acid uptake and enzyme activities in the lactating rat mammary gland.

The effects of chronic ethanol consumption on mammary gland amino acid uptake at the 15th day of lactation in the rat have been studied. Ethanol treatment decreased the arterial levels of Ala, Asp, Gly, Pro, Lys and Met, and increased those of Gln and alpha-amino-butyrate. Chronic ethanol treatment produced a decrease in the arteriovenous differences of Asp, Thr, Arg, Met and Phe, and increased those of Ala, Gln, Gly, Pro and Tyr. The combination of the calculated values of relative extraction and the arteriovenous differences indicate that these alterations in amino acid uptake are related to changes in the transport process for Ala, Asp, Thr, Pro, Arg, Asn, Gly, Tyr, and Phe, and that the alterations in the arteriovenous differences of Gln, Lys and Met are due to the affected arterial levels of these amino acids. Measurements of enzymatic activities in the mammary gland show that these alterations in the amino acid transport process cannot be ascribed to changes in the gamma-glutamyl cycle.

Amino Acids↗

PubMed1987

Chronic and acute ethanol impair the in vivo glucose uptake by lactating rat mammary gland.

Chronic and acute ethanol treatments increased the 3-hydroxybutyrate uptake by lactating rat mammary gland as a consequence of its high afferent concentration, without changing its relative extraction. The uptake of glucose was inhibited in the ethanol treated animals due to intrinsic alterations in the mammary gland metabolism as indicated by the decreased relative extraction and unchanged afferent concentration. These results would suggest that the elevated uptake of ketone bodies in ethanol-treated rats can be responsible, at least in part, for the decrease in glucose uptake by lactating rat mammary gland, although other direct effects of ethanol may be implied.

3-Hydroxybutyric Acid↗

PubMed1987

Hepatic uptake of gluconeogenic substrates in late-pregnant and mid-lactating rats.

Lactate uptake by liver is markedly increased in late-pregnant and mid-lactating rats without concomitant changes in its availability. Glycerol contribution to the liver 3-C unit uptake is only significant at term gestation (50% of lactate uptake) but almost negligible at mid-lactation (10% of lactate uptake). Pyruvate is only taken up by the liver of 15-day lactating rats. As a general trend, the livers of either pregnant or lactating rats are provided with an enhanced capacity to take up gluconeogenic substrates.

Animals↗

PubMed1987

Effects of chronic ethanol consumption on lactational performance in rat: mammary gland and milk composition and pups' growth and metabolism.

The effects of chronic ethanol consumption on lactational performance were studied in the rat on day 15 after delivery by determining mammary gland and milk composition, while growth rate and metabolic parameters were studied in pups coming from untreated mothers but being suckled by ethanol-treated mothers. Alcohol treatment increases the dry weight and lipoprotein lipase activity in the mammary gland, and decreases both absolute and relative mammary gland weight and mammary tissue protein content. The triacylglycerol concentration of milk from treated dams is increased, whereas lactose concentration is decreased in comparison to milk from controls, although the total energy content of milk from alcohol-treated dams is higher than that from controls. Ethanol treatment produces a reduction of daily milk production. Pups nursed by alcoholic mothers show a retarded growth with respect to pups nursed by untreated mothers. Furthermore, they present a reduction in the levels of circulating glucose, insulin, glycerol and free fatty acids, whereas an increase in acetoacetate and in urea levels is observed. Pups from alcoholic mothers show reduced glycogen concentration in the liver while the protein content is increased. Plasma free amino acids in pups nursed by alcoholic mothers are lower than in control pups, the differences in Ala, Glu+Gln, Gly, Pro, 4-OH-Pro, citrulline, Cys, Tyr, Phe and the combined total values being statistically significant. We may therefore draw the conclusion that chronic ethanol treatment impairs lactational performance affecting mammary gland function as shown by the decline in milk production and altered milk composition.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Drinking↗

PubMed1987

Some aspects of amino acid metabolism in the rat fetus.

1. In spite of an eventual catabolic phase during the last third of pregnancy, nitrogen retention seems to increase in pregnant rats. Furthermore, the high uterine blood flow and the high placental transfer of amino acids maintains an adequate nutrient supply to the fetuses. 2. The terminal rat fetus has a high circulating plasma amino acid level, as well as an increased free amino acid tissue pool when compared to its mother's. 3. In the rat fetus the development of enzymatic capabilities shows a sudden emergence (also denomined clustering) in late fetal life. In a general trend, the activities of enzymes related with amino acid metabolism are not well developed during rat fetal life. 4. The rate of amino nitrogen excretion in rat fetus is low, mainly due to the low development of urea cycle enzyme activities. 5. The rates of protein synthesis in many tissues are high in the rat fetus and they show a progressive decrease until delivery. On the other hand, the rates of protein breakdown are also higher during fetal life than in the adult.

Amino Acids↗

PubMed1987

Alanine uptake by liver at midpregnancy in rats.

The participation of the liver to the increase in alanine utilization seen at midpregnancy was studied in 9- and 12-day pregnant rats. Liver fractional extraction of alanine was assessed in vivo from the changes in concentration in afferent and efferent vessels. Hepatic active transport of alanine was determined in vitro using isolated plasma-membrane vesicles. Compared with nonpregnant controls, alanine fractional extraction was significantly increased on day 12 but not on day 9 of pregnancy. Vesicles isolated from 9- and 12-day pregnant animals had a greater capacity for Na+-dependent transport than those from controls. Eadie-Hofstee plotting showed that this increase was due to an increase in Vmax with no change in Km. Both A and ASC systems contributed to the Vmax increase. These results indicate that, although by day 9 the liver has developed an increased capacity for alanine uptake, the actual extraction is seen only by day 12 of pregnancy. At this stage the liver participates actively in the turnover of alanine and the development of hypoalaninemia.

Alanine↗

PubMed1987

Sulphur amino acid levels in some tissues of the rat during pregnancy and lactation.

Variations in free sulphur amino acid content in some rat tissues have been measured during pregnancy and lactation. As a general trend, sulphur amino acids tend to accumulate in tissues in late pregnancy. This accumulation is quantitatively more important in the liver and striated muscle than in the skin and the kidneys. Among sulphur amino acids, taurine shows the most marked changes, with a maximum accumulation in the liver and striated muscle on day 19 of pregnancy. After delivery, the levels of amino acids in the tissue pools show a tendency to drop, especially in liver and striated muscle. As expected, taurine shows the most marked decrease, returning to normal values in muscle but decreasing to depletion in the liver on day 20 after delivery. These results can be interpreted as follows: during pregnancy, increased food intake is sufficient to accommodate the metabolic needs of the mother, but during lactation, the requirements of milk synthesis promote the release of these amino acids from the tissues.

Amino Acids, Sulfur↗

PubMed1987

Variations in free amino acids in tissues of rats from birth to puberty.

Variations in concentrations of free amino acids and total protein in tissues of rats have been studied from birth to puberty. In the first 10 days after birth the concentrations of free amino acids in peripheral tissues increased. Only in the liver there was an increase in concentration of essential amino acids. When nutrition changed at weaning, concentration of amino acids decreased. This may be associated with high protein synthesis rates and increased catabolism of amino acids. Even after weaning, when the young rat became nutritionally independent, concentrations of free amino acids in the tissues had not become constant.

Aging↗

PubMed1986

Development of the gestational plasma hypoaminoacidemia in the rat.

The development of the gestational hypoaminoacidemia and the changes in amino acid blood compartmentation have been studied in virgin, 9 day, 12 day and 15 day pregnant rats. The drop of plasma amino acid levels is a rapid phenomenon which takes place between the 9th and the 12th day of pregnancy. It is mainly accounted for by gluconeogenic amino acids. Pregnant rats have lower plasma/cell amino acid ratios than virgin rats. Nine day pregnant rats have lower ratios than controls because of an important increase in the amino acid content of the cell fraction. Twelve and 15 day pregnant rats have lower ratios than controls because of the important drop in plasma levels, since cell content is similar to controls and lower than 9 day pregnant rats.

Amino Acids↗

PubMed1986

Tissue amino acid pool changes during the perinatal period of the rat.

Total free amino acid content in foetal liver, kidney, skin and striated muscle increases sharply during pregnancy. After delivery, there is no significant change in tissue total amino acid pools. The essential free amino acid pool in striated muscle decreases after delivery. This decrease suggests a relationship with the increased protein content in striated muscle.

Aging↗

PubMed1986

Effects of chronic ethanol ingestion on circulating metabolites and liver composition in the lactating rat.

A model of chronic ethanol administration has been used to study the effects of chronic ethanol consumption on the general metabolism of lactating rats on day 15 after delivery. We have studied the effects of ethanol on calories, food and fluid intake, body weight, circulating parameters such as glucose, glycerol, free fatty acids (FFA), triacylglycerols (TAG), amino acids (AA), ketone bodies, insulin and ethanol levels and liver composition. Chronic ethanol consumption markedly increases the levels of circulating B-OH-butyrate (B-OB-B), glycerol and FFA, while those of acetoacetate (AcAc), glucose, insulin and TAG remain constant. With the only exception of an increase in Glu + Gln levels, plasma AA decrease in the alcohol-treated rats, the change being significant for Ala, Pro, Lys, Arg, Val, Phe and 4-OH-proline. In the liver ethanol treatment causes an increment in TAG concentration and a decrease in glycogen content. In conclusion, chronic ethanol consumption produces notable alterations in the metabolism of lactating rats, which may diminish the efficiency of lactation, influencing milk production and, therefore, the pups' development.

Alcoholism↗