Alterations in mammary-gland blood flow and glucose metabolism in the lactating rat induced by short-term starvation and refeeding

1984 ◽  
Vol 4 (5) ◽  
pp. 421-426 ◽  
Author(s):  
Richard G. Jones ◽  
Dermot H. Williamson
Keyword(s):  
Blood Flow ◽  
Mammary Gland ◽  
Glucose Metabolism ◽  
Glucose Uptake ◽  
Limiting Factor ◽  
Short Term ◽  
Fed State ◽  
Substrate Supply ◽  
Lactating Mammary Gland ◽  
Rate Limiting

Six-hour starvation of lactating rats caused a 75% decrease in mammary-gland lipogenesis. The inhibition of lipogenesis was accompanied by a 45% decrease of blood flow to the mammary gland and a 60% decrease in glucose uptake. Within 2 h of refeeding, lipogenesis and glucose uptake by the gland increased to fed values though blood flow to the gland remained at only 63% of that in the fed state. It is concluded that blood flow, and hence substrate supply, is not a rate-limiting factor for lipogenesis by the lactating mammary gland in the rat.

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.

scholarly journals Role of fructose 2,6-bisphosphate in mammary gland of fed, starved and re-fed lactating rats

1985 ◽  
Vol 232 (3) ◽  
pp. 931-934 ◽  
Author(s):  
S Ward ◽  
N J Kuhn
Keyword(s):  
Mammary Gland ◽  
Intracellular Concentration ◽  
Limiting Factor ◽  
Maximal Rate ◽  
Physiological Conditions ◽  
Highly Sensitive ◽  
Lactating Mammary Gland ◽  
Rate Limiting

The fructose 2,6-bisphosphate (Fru-2,6-P2) content and intracellular concentration of lactating mammary gland was measured in fed, starved and re-fed rats. There was little or no change on starvation, and about 1.5-fold rise on re-feeding, contrasting with estimated glycolytic changes of about 10-fold. The 6-phosphofructokinase (PFK-1) activity of mammary extracts was highly sensitive to added Fru-2,6-P2 under all conditions examined, and appeared to approach saturation at physiological concentrations of this effector. The activity of mammary PFK-1 measured under optimal and ‘physiological’ conditions suggested that this enzyme operates in vivo at about 24% of maximal rate, and is likely to be an important rate-limiting factor in mammary glycolysis.

Blood flow and net amino acid uptake by the lactating mammary gland: effect of starvation

1985 ◽  
Vol 13 (5) ◽  
pp. 876-877 ◽  
Author(s):  
JUAN R. VIÑA ◽  
ARGIMIRO RODRIGUEZ ◽  
JUAN B. MONTORO ◽  
ANTONIO IRADI ◽  
INMACULADA R. PUERTES ◽  
...  
Keyword(s):  
Blood Flow ◽  
Mammary Gland ◽  
Amino Acid ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Lactating Mammary Gland

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 Monosaccharide transport in the mammary gland of the intact lactating rat

1984 ◽  
Vol 218 (1) ◽  
pp. 213-219 ◽  
Author(s):  
L C Threadgold ◽  
N J Kuhn
Keyword(s):  
Mammary Gland ◽  
Glucose Transport ◽  
Intracellular Water ◽  
Limiting Factor ◽  
Transport Capacity ◽  
Tissue Water ◽  
Monosaccharide Transport ◽  
Rate Limiting ◽  
Total Tissue

The Michaelis-Menten equation for the utilization of competing substrates was applied to the uptake of 2-deoxy[3H]glucose into the mammary gland of anaesthetized lactating rats. Intracellular water was calculated from total tissue water and sucrose space. Fed rats had a mean transport capacity of 2.2 mumol/min per g of tissue, giving an actual glucose transport in vivo of 1.1 mumol/min per g. Transport decreased by 90% on overnight starvation and returned to normal by 2 h of re-feeding. Similar changes were observed in the 1 min or 5 min transport of circulating 3-O-methylglucose. Transport of 3-O-methylglucose in starved rats was restored towards normal by insulin. In fed rats it increased between parturition and day 12 of lactation. The findings support the proposal that transport is a rate-limiting factor in the mammary utilization of carbohydrate.

Review: Current knowledge on mammary blood flow, mammary uptake of energetic precursors and their effects on sow milk yield

2008 ◽  
Vol 88 (2) ◽  
pp. 195-204 ◽  
Author(s):  
C. Farmer ◽  
N. L. Trottier ◽  
J. Y. Dourmad
Keyword(s):  
Blood Flow ◽  
Mammary Gland ◽  
Nutrient Availability ◽  
Glucose Transporter ◽  
Current Knowledge ◽  
Mammary Tissue ◽  
Energetic Efficiency ◽  
Limiting Factor ◽  
Vasoactive Substances ◽  
Endocrine Status

Dietary availability of nutrients to the mammary gland is a major limiting factor for sow milking potential. Nutrient availability to the udder is estimated by measuring mammary arteriovenous differences, which are affected by blood flow as well as circulating concentrations of nutrients. Mammary blood flow can be measured either directly or indirectly. Even though it is influenced by numerous factors, such as time since feeding, postural behavior, vasoactive substances, ambient temperature and litter size, authors report that the amount of plasma required to produce 1 kg of milk for a litter of 12 pigs ranges from 490 to 1050 L at peak lactation. Blood glucose is the major precursor for lactose synthesis and reported extraction rates of glucose by the mammary gland vary between 20 and 31%. Other metabolic precursors, such as triglycerides, phospholipids, acetate, propionate and lactate are also used for milk synthesis. There exists a discrepancy between estimates of energetic efficiency depending on the type of study conducted (metabolism vs. mammary balance). Endocrine status of the sow may affect mammary nutrient availability. There still exists a gap in our knowledge on relative mammary uptakes of energetic compounds other than glucose and on glucose transporter systems in porcine mammary tissue. The need for such information is of particular importance due to the increased milking demands currently made on lactating sows. Key words: Blood flow, lactation, mammary gland, nutrient uptake, sows

Effect of fasting and refeeding on mesenteric autoregulation in conscious rabbits

1992 ◽  
Vol 262 (5) ◽  
pp. H1407-H1414 ◽  
Author(s):  
J. W. Kiel ◽  
V. S. Bishop
Keyword(s):  
Blood Flow ◽  
Abdominal Aorta ◽  
Vena Cava ◽  
Celiac Artery ◽  
Minor Role ◽  
Short Term ◽  
Fed State ◽  
Fasting And Refeeding ◽  
A Minor ◽  
Conscious Animals

To determine whether feeding improves the efficacy of mesenteric autoregulation in conscious animals, rabbits were instrumented with pulsed-Doppler flow probes on the superior mesenteric artery and distal abdominal aorta to record mesenteric and hindquarters blood flow velocity. Hydraulic occluders were placed on the abdominal aorta (just below the celiac artery) and the thoracic vena cava to vary mesenteric and hindquarters arterial pressure (MAP), which was monitored via a catheter positioned in the distal abdominal aorta. Heart rate (HR) and lumbar sympathetic nerve activity (LSNA) were monitored as indexes of sympathetic nervous system activity. Pressure-velocity curves were obtained by aortic and caval occlusions on two consecutive days; first after a 24-h fast and after approximately 24 h of ad libitum refeeding. In the fed state, mesenteric velocity was significantly increased and MAP was decreased slightly; the slight decrease in MAP was counteracted by significant increases in HR and LSNA, whereas hindquarters perfusion was unchanged. The mesenteric and hindquarters pressure-velocity curves were all highly linear (r greater than or equal to 0.9) and showed no evidence of autoregulation in the fasted or fed state when pressure was changed by either the aortic or the caval occlusions. We conclude that autoregulation plays a minor role in the short-term regulation of mesenteric blood flow in the conscious rabbit.

scholarly journals Arteriovenous glucose differences across the mammary gland of the fed, starved, and re-fed lactating rat

1986 ◽  
Vol 239 (2) ◽  
pp. 269-274 ◽  
Author(s):  
T Page ◽  
N J Kuhn
Keyword(s):  
Fatty Acids ◽  
Mammary Gland ◽  
Glucose Uptake ◽  
Hepatic Glycogen ◽  
Similar Time ◽  
Fed State ◽  
Plasma Fatty Acids ◽  
Glucose Tolerance Tests ◽  
Time Courses

Arteriovenous glucose difference across the mammary gland of the lactating rat was used as an ‘instantaneous’ monitor of mammary glucose uptake. Plasma [glucose] and arteriovenous glucose difference varied according to whether Halothane, diethyl ether or sodium pentobarbitone anaesthesia was used. In pentobarbitone-treated rats a 60% glucose extraction in the fed state decreased to 5% after 18 h starvation, and recovered to 40% and 59% after 15 min and 60 min re-feeding respectively. The increase and decrease in plasma [fatty acids] and the depletion and restoration of hepatic glycogen mostly followed similar time courses. Re-feeding was accompanied by a brief surge of plasma [insulin]. Starved lactating rats showed a markedly greater capacity than age-matched virgin rats in the oral and intraperitoneal glucose tolerance tests. Mammary glucose uptake in the starved rat was significantly restored by oral or intraperitoneal glucose or by insulin, but not by acetoacetate or by heparin-induced elevation of plasma [fatty acids]. The role of insulin and of possible changes in mammary sensitivity to insulin in the return of mammary glucose uptake on re-feeding is discussed.

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 Regulation of Cerebral Glucose Metabolism in Normal and Polycythemic Newborn Lambs

1992 ◽  
Vol 12 (5) ◽  
pp. 856-865 ◽  
Author(s):  
Ted S. Rosenkrantz ◽  
Anthony F. Philipps ◽  
Isabella Knox ◽  
Edwin L. Zalneraitis ◽  
Patricia J. Porte ◽  
...  
Keyword(s):  
Blood Flow ◽  
Glucose Metabolism ◽  
Oxygen Uptake ◽  
Glucose Uptake ◽  
Glucose Concentration ◽  
Cerebral Glucose Metabolism ◽  
Control Group ◽  
Cerebral Oxygen ◽  
Independent Effects ◽  
Arterial Glucose

In contrast to previous investigations, a recent study of polycythemic lambs suggested that cerebral glucose delivery (concentration × blood flow), not arterial glucose concentration, determined cerebral glucose uptake. In the present study, the independent effects of arterial glucose concentration and delivery on cerebral glucose uptake were examined in two groups of chronically catheterized newborn lambs (control and polycythemic). Arterial glucose concentration was varied by an infusion of insulin. CBF was reduced in one group of lambs (polycythemic) by increasing the hematocrit. At all arterial glucose concentrations, the cerebral glucose delivery of the polycythemic group was 59.6% of the control group. At arterial glucose concentrations of > 1.6 mmol/L, cerebral glucose uptake was constant and similar in both groups. At arterial glucose concentrations of ≤1.6 mmol/L, cerebral glucose uptake was unchanged in the control group, but was significantly decreased in the polycythemic group. In contrast, the cerebral glucose uptake was similar in both groups over a broad range of cerebral glucose delivery values. At cerebral glucose delivery values ≤83 μmol/min/100 g, there was a significant decrease in cerebral glucose uptake in both groups. During periods of low cerebral glucose delivery and uptake, cerebral oxygen uptake fell in the control group but remained unchanged in the polycythemic group. Maintenance of cerebral oxygen uptake in the polycythemic group was associated with an increased extraction and uptake of lactate and β-hydroxybutyrate. We conclude that cerebral glucose delivery, not arterial glucose concentration alone, determines cerebral glucose uptake.

Sign in / Sign up

Export Citation Format

Share Document