1. Investigación

The effect of mild stress on various plasma metabolites in the rat has been studied. Mild stress resulted in significant decreases in liver size and glycogen content, as well as in an increase of blood glucose. In addition, plasma lactate, insulin, glycerol and urea, as well as a number of amino acids were altered by stress. These data indicate that minimal stress can have major effects upon the composition of blood, and suggest the need for strict rrecautions on the handling of animals during blood sampling. The site of blood extraction - tail tip i•s. neck - was also found to have a significant effect on plasma lactate. glucosi! and urea concentrations. In stressed animals the differences between tail- and neck blood composition were increased.

The 1,ffects 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 ct-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 acidE. Measurements of enzymatic activities in the mammary gland show that these alterations in the amino acid transport process cannot be ascribed to chan€eS in the ¥"-glutamyl cycle.

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 +Gin, 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. All these changes result in evident notable malnutrition in suckling young, which may be added to the negative effects of foetal development produced by maternal alcohol ingestion during pregnancy.

Se discuten las expresiones de actividad enzimatica mas utilizadas en estudios comparados de actividad en diferentes tejidos: microkatales por unidad de peso del tejido, por unidad de peso de proteina y por unidad de peso de AON. Se utiliza tambien la expresi6n de microkatales presentes en un 6rgano determinado referidos a unidad de peso del animal, 100 g en el caso de la rata. Las diversas expresiones se han aplicado a los niveles de aspartato transaminasa, glutamato deshidrogenasa y AMP desaminasa en higado, musculo estriado de pata trasera y riiiones de rata adulta. De Ios datos presentados se concluye que las mediciones de actividades enzimaticas en tejidos deben ser expresadas en mas de una forma, ya que la informaci6n obtenida a partir de una sola de ellas puede ser substancialmente distinta de la obtenida con otra de ellas, dando lugar a posibles conclusiones err6neas de! papel metab6lico jugado por el enzima en un tejido determinado.

I. 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. 2. We have studied the effects of ethanol on calorics, food and fluid intake. body weight, circulating parameters such as glucose, glycerol, free fatty acids (FFA). triacylglyccrots (TAG), amino ncids (AA), ketone bodies, insulin and ethanol levels and liver composition. 3. Chronic ethanol consumption markedly incrr.ascs the levels of circulating D-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 + Gin levels, plasma AA dccre;1se in the alcohol-treated rats, the change being significant for Ala, Pro, Lys, Alg, Val, Phe and 4-OH-poline. 4. In the liver ethanol treatment causes an increment in TAG concentration and a decrease in glycogen content. 5. In conclusion, chronic ethanol consumption produces notable alterations in the metabolism of lactating rats, which may diminish the efficiency (1f lactation, influencir g milk production and, therefore, the pups' development.

Chronic and acute ethanol treat nents increased th,: 3-hydroxybutyrate uptake by lactating rat mammary gland as :1 consequence of its high afferent concentration, without changing its relative extraction. The uptake of glucose was inhibited in the ethanol treated animals due to int ·insic alterations in the mammary gland metabolism as indicated by the decreased relative extrac1 ion and unchanged afferent concentration. These results would suggest that the ek:vated uptake of ketone bodies in ethanol-treated rats can be respcnsible, at least in part, for the decrease in glucose uptake by lactating rat mammary gland, although other direct effects of ethanol may be implied.

Plasma amino acid concentrations, together with other metabolic parameters were determined in thyroidectomized rats treated with daily injections of sal ins (hypothyroid), and 250 ,ug/kg L-T4 {hypothyroid). Data were compared with sham-operated controls. TherP. is a genera! incre'!SE> in plasma amino acid concentrations in hyperthyroidism, a limited in· crease only in several amino acid r.oncentrations in hypothyroid rats as compared with controls, and a considerable difference between the plasma aminograms of both groups. Amino acid homeostasis seems to be subject to greater modification in hyperthyroidism than in hypothyroidism.

The effects of food deprivation for up to 24 hours on plasma metabolic parameters in the rat have been studied. Liver dry weight and glycogen content dropped significantly from a hours of food deprivation onwards. Total muscle glycogen supplied about as much glycosyl residues or precursors as did the liver. Plasma glucose, urea, lactate and total and essential amino acids decreased significantly from 3 hours of fasting onwards. Glycerol, free fatty acids, beta-hydroxybutyrate and acetoacetate showed significant increases with fasting. Alanine, serine, arginine, threonine, aspartate plus asparagine and proline showed significant decreases with fasting. Several other amino acids showed almost nc change with fasting. Lysine, leucine plus isoleucine and taurine showed biphasic changes in their concentrations with a minimum at 6 hours and a transient recovery at 12 hours of fasting. Essential amino acids decreased more than the non essential ones. With fasting there is a shift in ammonia disposal with lower urea concentrations as nitrogen is better conserved. The results seem to suggest that there i~ a constant release of substrates, through liver and peripheral tissue proteolysis, that is counteracted by differential utilization of amino acids during fasting.

The effect of ethyl ether, pentobarbital sodium (Nembutal®) and chloral hydrate anesthesia on the concentrations of glucose, lactate, glycerol, insulin, individual amino acids and urea have been studied in rat plasma, as well as the glycogen content in the animal liver and striated muscle. Control animals were injected with saline solution. Two samples were taken from each animal at 15 and 30 minutes from the beginning of anesthesia. These samples were obtained from the cut tail's tip and from the neck wound produced by beheading the animal. Results show considerable differences between the three sets of animals and their controls as well as in their tail versus neck values. The overall effect of the three anesthetics used were roughly the same in spite of their different actions upon the different parameters studied. This was most marked in the aminograms. Significant changes induced were rather similar in number for all. The metabolite concentration profile in each situation may be used as a reference for possible artifacts induced by any experimental approach using these anesthetics.