scholarly journals Enzymic changes in rabbit and rat mammary gland during the lactation cycle

1969 ◽  
Vol 112 (3) ◽  
pp. 293-301 ◽  
Author(s):  
Bilquis Gul ◽  
R. Dils
Keyword(s):  
Mammary Gland ◽  
Malate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Pyruvate Carboxylase ◽  
Acid Synthesis ◽  
Mitochondrial Fraction ◽  
Soluble Form ◽  
Supernatant Fraction ◽  
Rat Mammary Gland ◽  
Lactation Cycle

1. Activities of glucose 6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), isocitrate dehydrogenase (EC 1.1.1.42), malate dehydrogenase (EC 1.1.1.37), malate dehydrogenase (decarboxylating) (EC 1.1.1.40), and pyruvate carboxylase (EC 6.4.1.1) were determined in subcellular fractions of mammary gland from rabbits during pregnancy, at different stages of lactation and during weaning. The results were compared with those obtained in similar experiments with rat mammary gland. 2. Three bases of expression of the activity of enzymes in the particle-free supernatant fraction of mammary gland were compared. During lactation, activity expressed per mg. of particle-free supernatant protein (uncorrected for milk protein) correlated well with that expressed per μg. of DNA phosphorus. The disadvantages of expressing activities per g. wet wt. are discussed. 3. The major differences between the two tissues were: (a) neither malate dehydrogenase (decarboxylating) nor a soluble form of pyruvate carboxylase could be detected in rabbit mammary gland at any stage of the lactation cycle; (b) isocitrate dehydrogenase increased in activity during lactation in rabbit mammary gland, but not in that of the rat. 4. Pyruvate carboxylase in the mitochondrial fraction of rabbit mammary gland, and in both the mitochondrial and the soluble fractions of rat mammary gland, did not change in activity during lactation. 5. For each tissue, the NADP-dependent dehydrogenases studied had a high activity at all stages of the lactation cycle compared with the rate of fatty acid synthesis at mid-lactation. The significance of these results is discussed with respect to the supply of NADPH via NADH.

scholarly journals Pyruvate carboxylase in lactating rat and rabbit mammary gland

1969 ◽  
Vol 111 (3) ◽  
pp. 263-271 ◽  
Author(s):  
Bilquis Gul ◽  
R. Dils
Keyword(s):  
Mammary Gland ◽  
Pyruvate Carboxylase ◽  
Freeze Drying ◽  
Specific Activity ◽  
Subcellular Fractionation ◽  
Mammary Glands ◽  
Mitochondrial Fraction ◽  
Freezing And Thawing ◽  
Rat Mammary Gland ◽  
Assay Conditions

1. Pyruvate carboxylase [pyruvate–carbon dioxide ligase (ADP), EC 6.4.1.1] was found in cell-free preparations of lactating rat and rabbit mammary glands, and optimum assay conditions for this enzyme were determined. 2. Subcellular-fractionation studies with marker enzymes showed pyruvate carboxylase to be distributed between the mitochondrial and soluble fractions of lactating rat mammary gland. Evidence is presented that the soluble enzyme is not an artifact due to mitochondrial damage. 3. In contrast, pyruvate carboxylase in lactating rabbit mammary gland is confined to the mitochondrial fraction. 4. The final product of pyruvate carboxylase action in the mitochondrial and particle-free supernatant fractions of lactating rat mammary gland was shown to be citrate. 5. The effects of freeze-drying, ultrasonic treatment and freezing-and-thawing on the specific activity of mitochondrial pyruvate carboxylase were investigated.

scholarly journals Phosphoribosyl pyrophosphate and phosphoribosyl pyrophosphate synthetase in rat mammary gland. Changes in the lactation cycle and effects of diabetes, insulin and phenazine methosulphate

1986 ◽  
Vol 238 (2) ◽  
pp. 553-559 ◽  
Author(s):  
S Kunjara ◽  
M Sochor ◽  
N Salih ◽  
P McLean ◽  
A L Greenbaum
Keyword(s):  
Mammary Gland ◽  
Fold Increase ◽  
Pentose Phosphate ◽  
Diabetic Rat ◽  
Synthetase Activity ◽  
Phosphoribosyl Pyrophosphate ◽  
Rat Mammary Gland ◽  
Lactation Cycle ◽  
Phenazine Methosulphate

Changes in the tissue content of phosphoribosyl pyrophosphate (PPRibP), glucose 6-phosphate, ribose 5-phosphate (Rib5P), RNA and DNA, of the activity of PPRibP synthetase (EC 2.7.6.1) and the conversion of [1-14C]- and [6-14C]-glucose into 14CO2 were measured at mid-lactation in the normal and diabetic rat and in pregnancy, lactation and mammary involution in the normal rat. The PPRibP, glucose 6-phosphate and Rib5P contents increase during pregnancy and early lactation to reach a plateau value at mid-lactation, before falling sharply during weaning. The PPRibP content, PPRibP synthetase activity and flux of glucose through the oxidative pentose phosphate pathway (PPP) all change in parallel during the lactation cycle. Similarly, after 3 and 5 days duration of streptozotocin-induced diabetes, ending on day 10 of lactation, there were parallel declines in PPRibP content, PPRibP synthetase and PPP activity. The effect of streptozotocin was prevented by pretreatment with nicotinamide and partially reversed by insulin administration. Addition of insulin to lactating rat mammary-gland slices incubated in vitro significantly raised the PPRibP content (+47%) and the activity of the PPP (+40%); phenazine methosulphate, which gives a 2-fold increase in PPP activity, raised the PPRibP content of lactating mammary gland slices by approx. 3-fold. It is concluded that Rib5P, generated in the oxidative segment of the PPP, is an important determinant of PPRibP synthesis in the lactating rat mammary gland and that insulin plays a central role in the regulation of the bioavailability of this precursor of nucleotide and nucleic acid synthesis.

NADP-linked dehydrogenases in secreted milk

1985 ◽  
Vol 52 (4) ◽  
pp. 501-506 ◽  
Author(s):  
Murray R. Grigor ◽  
Peter E. Hartmann
Keyword(s):  
Mammary Gland ◽  
Lactate Dehydrogenase ◽  
Malate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Malic Enzyme ◽  
Prolonged Storage ◽  
Phosphogluconate Dehydrogenase ◽  
The Absolute ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Accurate Reflection

SUMMARYThe activities of glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, isocitrate dehydrogenase, malic enzyme, lactate dehydrogenase and malate dehydrogenase have been determined in secreted milk from sows, rats and rabbits. Within each species, although there was considerable variation in the absolute activities of these enzymes, the relative activities were similar to those observed for, or previously published for mammary homogenates. The only exception was milk glucose 6-phosphate dehydrogenase which tended to lose activity upon prolonged storage in the mammary gland. These results suggest that the pattern of milk enzymes can be an accurate reflection of that occurring in the mammary gland.

Pyrimidine nucleotide synthesis in the rat mammary gland: Changes in the lactation cycle and effects of diabetes

1992 ◽  
Vol 48 (3) ◽  
pp. 263-274 ◽  
Author(s):  
Sirilaksana Kunjara ◽  
Milena Sochor ◽  
Michael Bennett ◽  
A.Leslie Greenbaum ◽  
Patricia McLean
Keyword(s):  
Mammary Gland ◽  
Nucleotide Synthesis ◽  
Pyrimidine Nucleotide ◽  
Rat Mammary Gland ◽  
Lactation Cycle

scholarly journals Rat mammary-gland acetyl-coenzyme A carboxylase. Interaction with milk fatty acids

1970 ◽  
Vol 118 (4) ◽  
pp. 645-657 ◽  
Author(s):  
A. L. Miller ◽  
Mary E. Geroch ◽  
H. Richard Levy
Keyword(s):  
Fatty Acids ◽  
Mammary Gland ◽  
Complex Mixture ◽  
Acid Synthesis ◽  
Acetyl Coa Carboxylase ◽  
High Concentration ◽  
Acetyl Coa ◽  
Milk Fatty Acids ◽  
Low Concentrations ◽  
Rat Mammary Gland

1. Highly purified rat mammary-gland acetyl-CoA carboxylase was inhibited by milk obtained from rats 12h after their young were weaned. 2. All the inhibitory activity was found in the particulate fraction (R105) obtained on centrifuging the milk. It could be extracted from milk fraction R105 with acetone and identified as a complex mixture of non-esterified fatty acids, present in high concentration (nearly 10mm) in the milk. 3. Inhibition of acetyl-CoA carboxylase was observed at low concentrations (0.2–20μm) of several of these fatty acids when fresh fully active enzyme was used. Enzyme that had been partly inactivated by aging, or by storing in the absence of citrate, was stimulated by low concentrations but inhibited by high concentrations of fatty acids. 4. Various experiments suggested that fatty acids produce irreversible inactivation of acetyl-CoA carboxylase. 5. The effects of palmitoyl-CoA on mammary-gland acetyl-CoA carboxylase were found to resemble those of fatty acids, except that palmitoyl-CoA was effective at lower concentration. 6. The effect of milk fraction R105 was tested on six other enzymes previously shown to decline to various extents after weaning. Although several of these enzymes were affected by unfractionated milk fraction R105, none was significantly inhibited by the acetone extract or by low concentrations of lauric acid. 7. The findings are consistent, both qualitatively and quantitatively, with a regulatory mechanism whereby milk fatty acids shut off fatty acid synthesis in the mammary gland after weaning by inhibiting acetyl-CoA carboxylase.

scholarly journals Activity of liver mitochondrial NAD+-dependent dehydrogenases of the krebs cycle in rats with acetaminophen-induced hepatitis developed under conditions of alimentary protein deficiency

2016 ◽  
Vol 62 (2) ◽  
pp. 169-172 ◽  
Author(s):  
O.N. Voloshchuk ◽  
G.P. Kopylchuk
Keyword(s):  
Malate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Control Level ◽  
Krebs Cycle ◽  
Fold Increase ◽  
Mitochondrial Fraction ◽  
Protein Deprivation ◽  
Drug Induced ◽  
Alimentary Protein Deficiency ◽  
Ketoglutarate Dehydrogenase

Activity of isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, malate dehydrogenase, and the NAD+/NADН ratio were studied in the liver mitochondrial fraction of rats with toxic hepatitis induced by acetaminophen under conditions of alimentary protein deprivation. Acetaminophen-induced hepatitis was characterized by a decrease of isocitrate dehydrogenase, a-ketoglutarate dehydrogenase and malate dehydrogenase activities, while the mitochondrial NAD+/NADН ratio remained at the control level. Modeling of acetaminophen-induced hepatitis in rats with alimentary protein caused a more pronounced decrease in the activity of NAD+-dependent dehydrogenases studied and a 2.2-fold increase of the mitochondrial NAD+/NADН ratio. This suggests that alimentary protein deprivation potentiated drug-induced liver damage

scholarly journals The intracellular location of pyruvate carboxylase, citrate synthase and 3-hydroxyacyl-CoA dehydrogenase in lactating rat mammary gland

1978 ◽  
Vol 171 (1) ◽  
pp. 273-275 ◽  
Author(s):  
D J Taylor ◽  
B Crabtree ◽  
G H Smith
Keyword(s):  
Mammary Gland ◽  
Pyruvate Carboxylase ◽  
Citrate Synthase ◽  
Extraction Technique ◽  
Intracellular Location ◽  
Rat Mammary Gland ◽  
Hydroxyacyl Coa Dehydrogenase

The intracellular location of pyruvate carboxylase (EC 6.4.1.1), citrate synthase (EC 4.1.3.7) and 3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35) in rat mammary gland was investigated by using a fractional-extraction technique. The results indicate a mitochondrial location for all three enzymes.

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