Changes in cathepsin D activity of maternal tissues during lactation and weaning in rats

Background. A loss of proteins from maternal tissues during lactation has been demonstrated. Protein loss could be explained by intracellular proteolysis. Methods. Cathepsin D activity was studied in the liver, muscle and mammary gland of lactating and weaned rat dams. Lactation was studied at maximal milk production (L-14) and at the final stage of lactation (L-21). Results. Basal activity (virgin rats) was three times higher in liver and mammary gland than in muscle. At both stages, L-14 and L-21, cathepsin D activity increased in liver (50 percent) as well as in the gland (164 percent), but no change was observed in muscle, when compared with controls. Twenty-four hours after litter separation, enzyme activity in the liver decreased to basal levels, while in the mammary gland cathepsin D activity showed a significant decrease but remained higher than control levels. Conclusion. Our results show that liver exhibits adaptive changes in the catabolism of proteins in response to the increased demands imposed by laction on the maternal organism, and when the stimuli disappear activity returns to basal levels. The high activity in mammary gland indicates fast turnover of structures and biomolecules as an answer to the high synthetic activity this tissue. Activity remained higher in the weaning rats, as a result of the regression process which the mammary gland is undergoing

Alanine aminotransferase activity in mammary tissue, muscle and liver of dam rat during lactation and weaning

Transamination reaction is the first step in the catabolism of most of the L-amino acids. Alanine is an important molecule in the inter-organ nitrogen transport, conveying them from muscle to the liver Amino groups from this amino acid are generally first transferred to alfa-ketoglutarate in the cytosol of liver cells to form glutamate and leaving behing the corresponding alfa-keto acid analog. Measurements of the alanine aminotransferase (EC2.6.1.2.) activity were compared in liver, mammary gland an skeletal muscle in virgin, lactating and weaning dam rats. In this study liver was the principal tissue involved in alanine transamination, while muscle showed a reduction in the enzyme activity during lactation. Results indicate an increase in alanine aminotransferase activity in the mammary gland during lactation and weaning when compared with virgin rats. This suggest that mammary gland during lactation is an importan extra-hepatic tissue involved in the metabolism of alanine and probably shunted into hte pathways for amino group metabolism in terms of nitrogen economy

Characterization of a fluorometric method for lipoprotein lipase

A fluorometric assay for determining lipoprotein lipase (LpL) activity is described. Dibutyrilfluorescine (DBF) was used as substrate for the enzyme and the fluorescine liberated by enzymatic hydrolysis of the substrate was measured. Extracts of acetone powder from adipose tissue as an enzyme source showed characteristics of lipoprotein lipase activity, i.e., inhibition by NaCl and optimum activity in alkaline pH. There was close agreement in LPL activity when the same sample was measured simultaneously using either dibutyrilfluorescine or tri[9, 10 3H]oleylglycerol as substrate. The extent of inhibition of lipoprotein lipase by NaCl was similar with both methods. The fluorometric method detected changes in LPL activity in heart and adipose tissue realted to the nutritional status of the animal with the same specificity and sensitivity than did the radioactive method. The flluorometric method is as sensitive, less expensive and less time consuming than the radioactive method

Depuración plasmática de etanol y su excreción en la leche de mujeres rurales que consumen pulque / Ethanol plasma clearance and its milk excretion in rural lactating women who drink pulque

En San Mateo Capulhuac, estado de México es frecuente el consumo del aguamiel y su producto fermentado, el pulque, por las mujeres embarazadas y lactantes debido a que le atribuyen cualidades galactotróficas. En este estudio se midió el etanol ingerido con el pulque por 11 madres lactantes y su concentración en el plasma y en la leche. La máxima concentración de etanol en el plasma y la leche se alcanzó a los 60 minutos independientemente del volumen de pulque ingerido. Ambas concentraciones fueron similares. La depuración del etanol en la leche fue más lenta en los casos con concentración de etanol más elevados. En el grupo de menor consumo de pulque la concentración máxima de etanol en la leche fue de 8.4 ñ 3.0 mg/dL; el 57 por ciento desapareció a los 120 min. En el grupo de mayor consumo de pulque la concentración máxima de etanol en la leche fue de 26.2 ñ 7.0 mg/dL; a los 120 min solamente se había eliminado el 11 por ciento de esa concentración. El pulque proporcionó a las madres lactantes una ingesta adicional de 350 kcal/día, comparadas con las madres que no lo consumen, lo cual representa una suplementación energética