scholarly journals Utlization of d-3-hydroxy[3-14C]butyrate for lipogenesis in vivo in lactating rat mammary gland

1978 ◽  
Vol 176 (2) ◽  
pp. 635-638 ◽  
Author(s):  
A M Robinson ◽  
D H Williamson
Keyword(s):  
Mammary Gland ◽  
Ketone Body ◽  
Nutritional State ◽  
Insulin Deficiency ◽  
Short Term ◽  
Major Site ◽  
Lactating Mammary Gland ◽  
Rat Mammary Gland

Incorporation of D-3-hydroxy[3-14C]butyrate into lipid in vivo suggests that lactating mammary gland is a major site of ketone-body utilization. The incorporation decreases in short-term insulin deficiency (2h) and on starvation (24h), but increases again on refeeding (2h). The activity of cytosolic acetoacetyl-CoA synthetase parallels the changes in nutritional state, but is not affected by short-term insulin deficiency.

scholarly journals Regulation of lactating-rat mammary-gland lipogenesis by insulin and glucagon in vivo. The role and site of action of insulin in the transition to the starved state

1984 ◽  
Vol 223 (2) ◽  
pp. 345-351 ◽  
Author(s):  
R G Jones ◽  
V Ilic ◽  
D H Williamson
Keyword(s):  
Mammary Gland ◽  
Adaptive Mechanism ◽  
Intracellular Metabolite ◽  
Short Term ◽  
Regulatory Enzymes ◽  
Metabolite Concentrations ◽  
Site Of Action ◽  
Lactating Mammary Gland ◽  
Rat Mammary Gland

Starvation for 6h and 24h caused an 80% and 95% decrease in the rate of mammary-gland lipogenesis respectively in conscious lactating rats. 2. Plasma insulin concentrations decreased and circulating ketone-body concentrations increased with the length of starvation. 3. The inhibition of lipogenesis after 24h starvation was accompanied by increased concentrations of glucose, glucose 6-phosphate and citrate in the mammary gland. Qualitatively similar changes were observed after 6h starvation. 4. Infusion of insulin at physiological concentrations caused a 100% increase in the rate of lipogenesis in fed animals and partially reversed the inhibition of lipogenesis caused by starvation. 5. Infusion of insulin tended to reverse the changes seen in intracellular metabolite concentrations. 4. Infusion of glucagon into fed rats caused no change in the rates of lipogenesis in mammary gland, liver or white adipose tissue. 7. It is concluded that (a) insulin acts physiologically to regulate lipogenesis in the mammary gland, (b) hexokinase and phosphofructokinase are important regulatory enzymes in the short-term control of lipogenesis in the mammary gland, which are under the influence of insulin, and (c) the unresponsiveness of mammary-gland lipogenesis in vivo to infusions of glucagon is consistent with an adaptive mechanism which diverts substrate towards the lactating mammary gland and away from other tissues.

scholarly journals Lactating mammary gland of the rat: a potential major site of ketone-body utilization

1972 ◽  
Vol 128 (2) ◽  
pp. 459-460 ◽  
Author(s):  
M Ann Page ◽  
Dermot H Williamson
Keyword(s):  
Mammary Gland ◽  
Ketone Body ◽  
Major Site ◽  
Lactating Mammary Gland

scholarly journals Comparison of glucose metabolism in the lactating mammary gland of the rat in vivo and in vitro. Effects of starvation, prolactin or insulin deficiency

1977 ◽  
Vol 164 (1) ◽  
pp. 153-159 ◽  
Author(s):  
Alison M. Robinson ◽  
Dermot H. Williamson
Keyword(s):  
Mammary Gland ◽  
Treated Group ◽  
Suitable Model ◽  
Short Term ◽  
Lactating Mammary Gland ◽  
Group 3 ◽  
Lactate And Pyruvate ◽  
In Vitro Effects

1. Measurements of arteriovenous differences across mammary glands of normal and starved lactating rats, and lactating rats made short-term insulin-deficient with streptozotocin or prolactin-deficient with bromocryptine, showed that only in the starved animals was there a significant decrease in glucose uptake. This decrease was accompanied by release of lactate and pyruvate from the gland, in contrast with the uptake of these metabolites by glands of normal lactating rats. 2. There were no marked differences in metabolite concentrations in freeze-clamped glands in the four conditions studied, apart from a decrease in [lactate] and [pyruvate] and an increase in [glucose] in the glands of the streptozotocin-treated group. 3. Acini isolated from the glands of starved, insulin or prolactin-deficient rats had a higher production of lactate and pyruvate from glucose than did glands from normal rats; this is in agreement with the reported decrease in the proportion of active pyruvate dehydrogenase in these situations [Field & Coore (1976) Biochem. J.156, 333–337; Kankel & Reinauer (1976) Diabetologia12, 149–154]. 4. Addition of insulin did not increase the uptake of glucose by acini from normal glands, but it caused a significant increase in the utilization of glucose by acini from glands of starved rats. Insulin did not decrease the accumulation of lactate and pyruvate in any of the experiments. 5. It is concluded that isolated acini represent a suitable model for the study of mammary-gland carbohydrate metabolism in that they reflect metabolism of the gland in vivo.

scholarly journals Regulation of acetyl-CoA carboxylase in rat mammary gland. Effects of starvation and of insulin and prolactin deficiency on the fraction of the enzyme in the active form in vivo

1982 ◽  
Vol 204 (1) ◽  
pp. 273-280 ◽  
Author(s):  
Elizabeth M. McNeillie ◽  
Victor A. Zammit
Keyword(s):  
Mammary Gland ◽  
Enzyme Activities ◽  
Enzyme Concentration ◽  
Acetyl Coa Carboxylase ◽  
Initial Activity ◽  
Acetyl Coa ◽  
Activity Ratios ◽  
Rat Mammary Gland ◽  
Rate Limiting

The ‘initial’ (I), endogenous phosphatase-activated (A) and citrate-activated (C) activities of acetyl-CoA carboxylase were measured in mammary-gland extracts of pregnant and lactating rats. There was a 10-fold increase in the A and C enzyme activities in the transition from early to peak lactation [cf. data of Mackall & Lane (1977) Biochem. J.162, 635–642], but there was no significant increase in the ratio of the initial activity to the A and C activities of the enzyme. Starvation (24h) or short-term (3h) streptozotocin-induced diabetes both resulted in a 40% decrease in I/A and I/C activity ratios. In starvation this was accompanied by a decrease in the absolute values of the A and C activities such that the initial activity in mammary glands of starved animals was 45% that in glands from fed animals. Insulin treatment of starved or diabetic animals 60min before killing increased the I activity without affecting the A or C enzyme activities. Removal of the pups for 24h from animals in peak lactation (weaning) resulted in a marked but similar decrease in all three activities such that, although the initial activity was only 10% of that in suckled animals, the I/A and I/C activity ratios remained high and unaltered. Inhibition of prolactin secretion by injection of 2-bromo-α-ergocryptine gave qualitatively similar results to those during weaning. Simultaneous administration of ovine prolactin completely prevented the effects of bromoergocryptine. It is suggested that the initial activity of acetyl-CoA carboxylase in rat mammary gland is regulated by at least two parallel mechanisms: (i) an acute regulation of the proportion of the enzyme in the active state and (ii) a longer-term modulation of enzyme concentration in the gland. Insulin appeared to mediate its acute effects through mechanism (i), whereas prolactin had longer-term effects on enzyme concentration in the gland. A comparison of initial enzyme activities (I) obtained in the present study with rates of lipogenesis measured in vivo [Agius & Williamson (1980) Biochem. J.192, 361–364; Munday & Williamson (1981) Biochem. J.196, 831–837] gave good agreement between the two sets of data for all conditions studied except for 24h-starved and streptozotocin-diabetic animals. It is suggested that acetyl-CoA carboxylase activity is rate-limiting for lipogenesis in the mammary gland in normal, fed, suckled or weaned animals but that in starved and short-term diabetic animals changes in the activity of the enzyme by covalent modification alone may not be sufficient to maintain the enzyme in its rate-limiting role.

Utilization of dipeptides by the caprine mammary gland for milk protein synthesis

1994 ◽  
Vol 267 (1) ◽  
pp. R1-R6 ◽  
Author(s):  
F. R. Backwell ◽  
B. J. Bequette ◽  
D. Wilson ◽  
A. G. Calder ◽  
J. A. Metcalf ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Mammary Gland ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Milk Protein ◽  
Common Mechanism ◽  
Dairy Goats ◽  
Peptide Hydrolysis ◽  
Lactating Mammary Gland

Specific use by the mammary gland in vivo of amino acids (AA) of peptide origin has been demonstrated in lactating dairy goats using a dual-labeled tracer technique involving close-arterial (external pudic artery, EPA) infusion of 13C-labeled dipeptides. The extent of utilization does not appear to differ for glycyl-L-[1-13C]phenylalanine and glycyl-L-[1-13C]leucine, perhaps indicative of a common mechanism by which AA are incorporated from peptide into milk protein. [1-13C]phenyl-alanine of peptide origin appears to be concentrated within the red blood cell, suggesting a role for the erythrocyte in peptide metabolism in vivo. In conclusion, it appears that the lactating mammary gland of goats has the ability to utilize AA of peptide origin for milk protein synthesis, and while the mechanism by which [1-13C]AA are incorporated into milk protein is not clear, it may involve peptide hydrolysis by either mammary cell surface or red blood cell hydrolases followed by uptake of liberated AA by the mammary gland.

A distal region, hypersensitive to DNase I, plays a key role in regulating rabbit whey acidic protein gene expression

2001 ◽  
Vol 359 (3) ◽  
pp. 557-565 ◽  
Author(s):  
Benjamin MILLOT ◽  
Marie-Louise FONTAINE ◽  
Dominique THEPOT ◽  
Eve DEVINOY
Keyword(s):  
Mammary Gland ◽  
Sequence Similarity ◽  
Distal Region ◽  
Dnase I ◽  
Whey Acidic Protein ◽  
Acidic Protein ◽  
Upstream Region ◽  
Lactating Mammary Gland

The aim of the present study was to identify the functional domains of the upstream region of the rabbit whey acidic protein (WAP) gene, which has been used with considerable efficacy to target the expression of several foreign genes to the mammary gland. We have shown that this region exhibits three sites hypersensitive to DNase I digestion in the lactating mammary gland, and that all three sites harbour elements which can bind to Stat5 in vitro in bandshift assays. However, not all hypersensitive regions are detected at all stages from pregnancy to weaning, and the level of activated Stat5 detected in the rabbit mammary gland is low except during lactation. We have studied the role of the distal site, which is only detected during lactation, in further detail. It is located within a 849bp region that is required to induce a strong expression of the chloramphenicol acetyltransferase reporter gene in transfected mammary cells. Taken together, these results suggest that this region, centred around a Stat5-binding site and surrounded by a variable chromatin structure during the pregnancy–lactation cycle, may play a key role in regulating the expression of this gene in vivo. Furthermore, this distal region exhibits sequence similarity with a region located around 3kb upstream of the mouse WAP gene. The existence of such a distal region in the mouse WAP gene may explain the differences in expression between 4.1 and 2.1kb mouse WAP constructs.

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

1987 ◽  
Vol 7 (10) ◽  
pp. 777-781 ◽  
Author(s):  
S. Vilaró ◽  
O. Viñas ◽  
E. Herrera ◽  
X. Remesar
Keyword(s):  
Mammary Gland ◽  
Glucose Uptake ◽  
Ketone Bodies ◽  
Direct Effects ◽  
Acute Ethanol ◽  
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.

scholarly journals Reciprocal changes in amino acid metabolism in mammary gland and liver of the lactating rat on starvation and refeeding as indicated by the tissue accumulation of α-amino[1-14C]isobutyrate

1990 ◽  
Vol 268 (3) ◽  
pp. 799-802 ◽  
Author(s):  
A E Tedstone ◽  
V Ilic ◽  
D H Williamson
Keyword(s):  
Amino Acids ◽  
Mammary Gland ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Reciprocal Relationship ◽  
Nutritional State ◽  
Tissue Accumulation

Measurements of the tissue accumulation in vivo and in vitro by hepatocytes and mammary-gland acini of alpha-amino[1-14C]isobutyrate ([1-14C]AIB) were compared in virgin and lactating rats. The results indicate the existence of a reciprocal relationship between mammary gland and liver for AIB accumulation that is dependent on the lactational and the nutritional state of the rat. This suggests that amino acids are preferentially directed to the mammary gland during active lactation.

scholarly journals Acetate metabolism in lactating sheep

1982 ◽  
Vol 48 (2) ◽  
pp. 319-328 ◽  
Author(s):  
D. W. Pethick ◽  
D. B. Lindsay
Keyword(s):  
Blood Flow ◽  
Mammary Gland ◽  
Lactate Production ◽  
Utilization Rate ◽  
Acetate Metabolism ◽  
Oxygen Utilization ◽  
Milk Flow ◽  
Lactating Mammary Gland ◽  
Acetate Utilization

1. The metabolism of acetate, glucose and D(−)-3-hydroxybutyrate was studied in lactating and non lactating sheep in vivo. Special consideration was given to the utilization by hind-limb muscle in both groups of sheep and the uptake of nutrients by the lactating mammary gland was also measured.2. The entry of acetate into the circulation (mmol/h per kg body-weight) was similar in all experimental animals at a given arterial concentration of acetate. However, normal lactation was associated with a reduced extraction of acetate by muscle and the 'spared' acetate was comparable with that removed by the udder. Feeding lactating ewes a 700 g concentrate/kg ration tended to prevent this redistribution of acetate utilization.3. The muscle of non-lactating ewes utilized sufficient glucose, when corrected for lactate release, to account for 57% of the oxygen utilization by muscle. In lactation this fell to 32%, largely because of an increased lactate production. D(−)-3-Hydroxybutyrate utilization by muscle accounted for 16–17% of the O2 consumed by the muscle in non-lactating and lactating sheep.4. Lactating mammary gland metabolism in sheep was similar to published values for dairy cows and goals. Thus the extraction (%) of glucose, O2, acetate and D(−)-3-hydroxybutyrate was 25, 28, 62 and 53 respectively. Blood flow was 529 ml/min per kg udder and the ratio blood flow: milk flow was 475. Glucose used by the udder relative to the whole animal utilization rate may be less in sheep than in cows and goats, but the comparable proportion for acetate is as large or larger than in these species.

scholarly journals Control of glucose metabolism in isolated acini of the lactating mammary gland of the rat. The ability of glycerol to mimic some of the effects of insulin

1977 ◽  
Vol 168 (3) ◽  
pp. 465-474 ◽  
Author(s):  
A M Robinson ◽  
D H Williamson
Keyword(s):  
Mammary Gland ◽  
Glucose Metabolism ◽  
Glucose Uptake ◽  
Glucose Utilization ◽  
Homogeneous Population ◽  
Furoic Acid ◽  
Lactating Mammary Gland ◽  
Rat Mammary Gland ◽  
Pyruvate Ratio

Inhibition of glucose uptake by acetoacetate and relief of this inhibition by insulin found previously in slices of rat mammary gland [Williamson, McKeown & Ilic (1975) Biochem. J. 150. 145-152] was confirmed in acini, which represent a more homogeneous population of cells. Glycerol (1mM) behaved like insulin (50 minuits/ml) in its ability to relieve the inhibition of glucose (5 mM) utilization caused by acetoacetate (2 mM) in acini. Both glycerol and insulin reversed the increase in [citrate] and the decrease in [glycerol 3-phosphate] and the [lactate]/[pyruvate] ratio in the presence of acetoacetate. Lipogenesis from 3H2O, [3-14C] acetoacetate, [1-14C]- and [6-14C]-glucose was stimulated, whereas 14CO2 formation from [3-14C]acetoacetate was decreased. Neither insulin nor glycerol relieved the acetoacetate inhibition of glucose uptake when lipogenesis was inhibited by 5-(tetradecyloxy)-2-furoic acid. From measurements of [3-14C]acetoacetate incorporation into lipid in the various situations it is suggested that a cytosolic pathway for acetoacetate utilization may exist in rat mammary gland. In the absence of acetoacetate, glycerol inhibited glucose utilization by 60% and increased both [glycerol 3-phosphate] and the [lactate/[pyruvate] ratio. Possible ways in which glycerol may mimic the effects of insulin are discussed.

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