Estimations of Rates of Synthesis and Degradation of Several Rat Mammary Gland Enzymes from Changes in Enzyme Activities

1972 ◽  
Vol 50 (4) ◽  
pp. 386-391 ◽  
Author(s):  
G. O. Korsrud ◽  
R. L. Baldwin
Keyword(s):  
Fatty Acid ◽  
Malic Enzyme ◽  
Fatty Acid Synthetase ◽  
Mammary Glands ◽  
Phosphogluconate Dehydrogenase ◽  
Udpglucose Pyrophosphorylase ◽  
Cleavage Enzyme ◽  
Rat Mammary Gland ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Synthesis And Degradation

Based upon rates of decrease in the activities of citrate cleavage enzyme (EC 4.1.3.7), malic enzyme (EC 1.1.1.40), fatty acid synthetase, UDPglucose pyrophosphorylase (EC 2.7.7.9), UDPglucose 4-epimerase (EC 5.1.3.3), and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) in rat mammary glands after adrenalectomy–ovariectomy on the 11th day of lactation, the half-lives of the enzymes were estimated to be 28, 31, 28, 50, 20, and 24 h, respectively. The half-life estimates for UDPglucose pyrophosphorylase and glucose-6-phosphate dehydrogenase compared favorably with previous estimates of 35 and 20 h, respectively, obtained in rats 5 days postpartum utilizing specific immunological techniques. In a second experiment, increases in the activities of enzymes in adrenalectomized, lactating rats after initiation of cortisol therapy were investigated. Rats were adrenalectomized on the 5th day of lactation and cortisol therapy was started 5 days later. The estimated half-lives for citrate cleavage enzyme, malic enzyme, fatty acid synthetase, UDPglucose pyrophosphorylase, UDPglucose 4-epimerase, the A protein of the lactose synthetase complex, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase (EC 1.1.1.44), and hexokinase (EC 2.7.1.1) were, respectively, 84, 60, 92, 76, 170, 102, 79, 88, and 81 h.

Effects of Adrenalectomy, Adrenalectomy–Ovariectomy, and Cortisol and Estrogen Therapies Upon Enzyme Activities in Lactating Rat Mammary Glands

1972 ◽  
Vol 50 (4) ◽  
pp. 366-376 ◽  
Author(s):  
G. O. Korsrud ◽  
R. L. Baldwin
Keyword(s):  
Pyruvate Kinase ◽  
Enzyme Activities ◽  
Secretory Cell ◽  
Succinic Dehydrogenase ◽  
Mammary Glands ◽  
Pentose Phosphate ◽  
Phosphogluconate Dehydrogenase ◽  
Udpglucose Pyrophosphorylase ◽  
Cleavage Enzyme ◽  
Glucose 6 Phosphate Dehydrogenase

The effects of adrenalectomy and adrenalectomy–ovariectomy on the 5th day of lactation followed by cortisol and estrogen therapies on enzyme activities in rat mammary glands were investigated. This stage of lactation was selected because mammary secretory cell proliferation is essentially complete at this time thereby enabling study of the effects of cortisol and estrogen on enzyme levels in a nonproliferating secretory cell population. Eighteen enzymes were selected for study on the bases of their respective roles in milk biosynthesis and carbohydrate and energy metabolism and/or on the basis of previous studies indicating that their activities increase during midlactation or are regulated, in part, by steroid hormones. After adrenalectomy on the 5th day of lactation, cortisol therapy was required for normal increases in the activities of succinic dehydrogenase, citrate cleavage enzyme, malic enzyme, UDPglucose pyrophosphorylase, UDPglucose 4-epimerase, and glucose-6-phosphate dehydrogenase. The activities of UDPglucose pyrophosphorylase and glucose-6-phosphate dehydrogenase were higher than normal in cortisol-treated animals. Cortisol therapy during the last 2 days of the experiment increased the activity of UDPglucose pyrophosphorylase and possibly citrate cleavage enzyme. The activities of α-glycerolphosphate dehydrogenase, phosphoglucomutase, 6-phosphogluconate dehydrogenase, pentose phosphate metabolizing ability, hexokinase, phosphofructokinase, fructose-1,6-diphosphate aldolase, pyruvate kinase, lactic dehydrogenase, aspartate aminotransferase, isocitrate dehydrogenase, and extramitochondrial malate dehydrogenase were not notably affected by adrenalectomy or cortisol therapy. The activities of 6-phosphogluconate dehydrogenase, pentose phosphate metabolizing ability, phosphofructokinase, and pyruvate kinase may have increased after the 5th day of lactation in adrenalectomized as well as in normal animals. Combining ovariectomy with adrenalectomy reduced pup weight gains more than adrenalectomy alone, but did not further decrease significantly the activities of any of the enzymes measured. Ovariectomy had no effect when cortisol was administered. Cortisol therapy completely reversed adverse effects of estrogen given to adrenalectomized–ovariectomized animals. On the bases of these and previous data, it was concluded that cortisol regulates the rates of synthesis of several mammary gland enzymes during midlactation.

scholarly journals The role of dietary protein in hepatic lipogenesis in the young rat

1981 ◽  
Vol 45 (3) ◽  
pp. 529-538 ◽  
Author(s):  
G. R. Herzberg ◽  
Minda Rogerson
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Dietary Protein ◽  
Fatty Acid Synthetase ◽  
Acid Synthesis ◽  
Hepatic Lipogenesis ◽  
Hepatic Fatty Acid ◽  
Cleavage Enzyme ◽  
Glucose 6 Phosphate Dehydrogenase

1. The effect of varying dietary levels of casein (40–140 g/kg) on hepatic lipogenesis and the levels of hepatic fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD), malic enzyme (EC 1.1.1.40; ME), citrate cleavage enzyme (EC 4.1.3.8;CCE), acetyl CoA carboxylase (EC 6.4.1.2; AcCx), glucokinase (EC 2.7.1.2; GK), and pyruvate dehydrogenase (PDH) was examined in young, growing rats.2. The activities of AcCx, FAS, G6PD and in vivo fatty acid synthesis were generally found to increase with increased dietary protein.3. The levels of GK and PDH were not related to dietary protein.4. ME decreased with increasing dietary protein.5. The results demonstrate a dissociation between hepatic fatty acid synthesis and ME and suggest that when rats consume low-protein diets the NADPH needed for fatty acid synthesis is generated primarily by ME but that as the level of dietary protein is increased the contribution of ME is reduced while that of the phosphogluconate pathway becomes more important.

scholarly journals Regulation of hepatic lipogenesis by dietary maize oil or tripalmitin in the meal-fed mouse

1980 ◽  
Vol 43 (3) ◽  
pp. 571-579 ◽  
Author(s):  
G. R. Herzberg ◽  
N. Janmohamed
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Malic Enzyme ◽  
Fatty Acid Synthetase ◽  
Acid Synthesis ◽  
Hepatic Lipogenesis ◽  
Meal Feeding ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Maize Oil

The effect of varying dietary levels of maize oil and tripalmitin (0–250 g fat/kg) on hepatic lipogenesis and the levels of hepatic fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD), malic enzyme (EC 1.1.1.38, 1.1.1.39, 1.1.1.40; ME) and glucokinase (EC 2.7.1.2; GK) was examined in meal-fed mice.2. Meal-fed mice compared to mice fed ad lib. show enhanced hepatic lipogenesis as demonstrated by an increased rate of in vivo fatty acid synthesis and increased levels of FAS, ME and G6PD. The level of GK in meal-fed mice was unchanged by meal feeding.3. Maize oil more effectively reduced in vivo hepatic lipogenesis than tripalmitin in meal-fed mice.4. Maize oil more effectively reduced the hepatic levels of FAS, G6PD, ME and GK than tripalmitin in meal-fed mice.5. The increased inhibition by maize oil is observed at all levels of fat in the diet investigated and has been shown not to be due to decreased carbohydrate intake nor to differences between the absorption of maize oil and tripalmitin.

The Effects of Catecholamines, Glucagon, and Diet on Enzyme Activities in Brown Fat and Liver of the Rat

1974 ◽  
Vol 52 (9) ◽  
pp. 739-743 ◽  
Author(s):  
Peter Hahn ◽  
Lorne T. Kirby
Keyword(s):  
Body Weight ◽  
Fatty Acid ◽  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Fatty Acid Synthetase ◽  
High Carbohydrate Diet ◽  
Brown Fat ◽  
Carbohydrate Diet ◽  
High Carbohydrate ◽  
Cleavage Enzyme

The effects of a high carbohydrate diet fed to young rats for 24–48 h on phosphoenolpyruvate carboxykinase, malic enzyme, citrate-cleavage enzyme, and fatty acid synthetase could be overcome by injecting the animals with glucagon (1 mg/100 g body weight) or norepinephrine (20 μg/100 g body weight) four times a day. The same effect was achieved with 50 mg ephedrine added to the 24 h diet. The catecholamines were more effective in brown fat, whereas glucagon seemed somewhat more effective in the liver.

scholarly journals Effect of thyroidectomy on pathways of glucose metabolism in lactating rat mammary gland

1967 ◽  
Vol 105 (2) ◽  
pp. 615-623 ◽  
Author(s):  
Eileen Walters ◽  
Patricia McLean
Keyword(s):  
Mammary Gland ◽  
Glucose Oxidation ◽  
Mammary Tissue ◽  
Control Group ◽  
Phosphogluconate Dehydrogenase ◽  
Lactating Mammary Gland ◽  
Cleavage Enzyme ◽  
Rat Mammary Gland ◽  
Group 3 ◽  
Glucose 6 Phosphate Dehydrogenase

1. Assessment of the overall metabolic changes in lactating mammary gland after thyroidectomy has been made by measurement of the incorporation of 14C from specifically labelled glucose, pyruvate and acetate into 14CO2 and 14C-labelled lipid in the experimental rats and in sham-operated control animals. 2. Thyroidectomy depressed the oxidation of 14C-labelled substrates, an effect still apparent when the control rats were pair-fed with thyroidectomized rats; however, the ratio of oxidation of [1−14C]glucose/oxidation of [6−14C]glucose was unaltered. In parallel with these studies it was revealed that the activities of hexokinase, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and NADP-linked isocitrate dehydrogenase were all lower in the thyroidectomized group than in the pair-fed control group. 3. Thyroidectomy also lowered the incorporation of 14C-labelled substrates into 14C-labelled lipid, an effect further studied by measurement of the activities of citrate-cleavage enzyme and acetate thiokinase. Restricting the food intake of the control rats to that of the thyroidectomized group lowered the activity of citrate-cleavage enzyme, but no further depression was observed on thyroidectomy. The oxidized and reduced nicotinamide nucleotide content of mammary tissue was shown to be decreased in the thyroidectomized rats compared with the control rats.

scholarly journals Lipid metabolism by rat lung in vitro. Effect of starvation and re-feeding on utilization of [U-14C]glucose by lung slices

1971 ◽  
Vol 124 (2) ◽  
pp. 257-264 ◽  
Author(s):  
Richard W. Scholz ◽  
Rodney A. Rhoades
Keyword(s):  
Fatty Acid ◽  
Isocitrate Dehydrogenase ◽  
Malic Enzyme ◽  
Total Phospholipid ◽  
Fatty Acid Fraction ◽  
Acid Fraction ◽  
Phosphogluconate Dehydrogenase ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Vitro Effect

1. The incorporation of [U-14C]glucose into several lipid components of lung and liver slices, and the activities of glucose 6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), ‘malic’ enzyme (EC 1.1.1.40) and NADP–isocitrate dehydrogenase (EC 1.1.1.42) of the cell cytosol were examined in normal, starved and re-fed rats. 2. Lipogenesis and the activities of these enzymes in liver were decreased markedly in rats starved for 72h. Re-feeding starved rats on a fat-free diet for 72h resulted in the well documented hyperlipogenic response in liver, particularly in its ability to convert glucose into neutral lipid, and increased activities of glucose 6-phosphate dehydrogenase, ‘malic’ enzyme and 6-phosphogluconate dehydrogenase to values approx. 700, 470 and 250% of controls respectively. 3. Approx. 70% of the total label in lung lipids was present in the phospholipid fraction. Hydrolysis of lung phospholipids revealed that lipogenesis from glucose was considerable, with approx. 40% of the total phospholipid radioactivity present in the fatty acid fraction. 4. Incorporation of glucose into total lung lipids was decreased by approx. 40% in lung slices of starved rats and was returned to control values on re-feeding. Although phospholipid synthesis from glucose was decreased in lung slices of starved rats, the decrease proportionally was greater for the fatty acid fraction (approx. 50%) as compared with the glycerol fraction (approx. 25%). 5. The activities of lung glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and NADP–isocitrate dehydrogenase were not affected by the dietary alterations. ‘Malic’ enzyme activity was not detected in lung cytosol preparations. 6. The results are discussed in relation to the surface-active lining layer (surfactant) of the lung.

scholarly journals Regulation of lipogenic capacity in lactating rats

1982 ◽  
Vol 208 (3) ◽  
pp. 611-618 ◽  
Author(s):  
M R Grigor ◽  
A Geursen ◽  
M J Sneyd ◽  
S M Warren
Keyword(s):  
Mammary Gland ◽  
Fatty Acid ◽  
Malic Enzyme ◽  
Fatty Acid Synthase ◽  
Specific Activity ◽  
Mammary Glands ◽  
Lipogenic Enzymes ◽  
Pregnancy And Lactation ◽  
Specific Activities

1. The rate of mammary-gland lipogenesis measured in vivo from 3H2O was suppressed after decreasing the milk demand by decreasing the number of pups from ten to two or three, as well as by giving diets containing lipid [Grigor & Warren (1980) Biochem. J. 188, 61-65]. 2. The specific activities of the lipogenic enzymes fatty acid synthase, glucose 6-phosphate dehydrogenase and ‘malic’ enzyme increased between 6- and 10-fold in the mammary gland and between 2- and 3-fold in the livers during the first 10 days of lactation. The increases in specific activity coupled with the doubling of liver mass which occurred during pregnancy and lactation resulted in considerable differences in total liver activities when compared with virgin animals. 3. Although consumption of a diet containing 20% peanut oil suppressed the activities of the three lipogenic enzymes in the livers, only the ‘malic’ enzyme was affected in the mammary glands. 4. In contrast, decreased milk demand did not affect the specific activities of any of the liver enzymes, whereas it resulted in suppression of all three lipogenic enzymes of the mammary glands. There was no effect on either the cytoplasmic malate dehydrogenase or the lactate dehydrogenase of the mammary gland. 5. In all the experiments performed, the activity of the fatty acid synthase correlated with the amount of material precipitated by the rabbit antibody raised against rat fatty acid synthase.

scholarly journals Hepatic lipogenesis in young rats given proteins of different quality

1984 ◽  
Vol 52 (1) ◽  
pp. 131-137 ◽  
Author(s):  
G. R. Herzberg ◽  
Minda Rogerson
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Protein Quality ◽  
Fatty Acid Synthetase ◽  
Acid Synthesis ◽  
Hepatic Lipogenesis ◽  
Atp Citrate Lyase ◽  
Specific Activities ◽  
Glucose 6 Phosphate Dehydrogenase

1. The effect of feeding casein, lactalbumin, soya-bean protein, gluten or gelatin on hepatic lipogenesis and the levels of hepatic fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (EC 1. 1. 1.49; G6PD), malic enzyme (EC 1. 1. 1.40; ME) ATP-citrate lyase (EC 4. 1. 3. 8; CL), acetyl CoA carboxylase (EC 6.4.1.2; ACCx) and glucokinase (EC 2. 7. 1. 2; GK) was examined in young growing rats.2. The total activities of ACCx, FAS, CL, GK, G6PD, GK, ME and fatty acid synthesis in vivo were positively correlated with protein quality.3. The specific activities of ACCx, FAS, CL, G6PD and fatty acid synthesis in vivo were positively correlated with protein quality.4. The specific activities of GK and ME were unrelated to protein quality.5. The results demonstrate a dissociation between ME and hepatic lipogenesis and suggest a role for the NADPH generated by ME which is not related to the needs of fatty acid synthesis.

The Isolation and Characterization of Fatty-Acid-Synthetase mRNA from Rat Mammary Gland

1981 ◽  
Vol 114 (3) ◽  
pp. 643-651 ◽  
Author(s):  
John S. MATTICK ◽  
Zendra E. ZEHNER ◽  
Michael A. CALABRO ◽  
Salih J. WAKIL
Keyword(s):  
Mammary Gland ◽  
Fatty Acid ◽  
Fatty Acid Synthetase ◽  
Isolation And Characterization ◽  
Rat Mammary Gland
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