Parallel measurements of heat production and thermogenin content in brown fat cells during cold acclimation of rats

1986 ◽  
Vol 6 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Erik Steen Hansen ◽  
Jens Knudsen
Keyword(s):  
Cold Acclimation ◽  
Heat Production ◽  
Continuous Flow ◽  
Specific Protein ◽  
Competitive Elisa ◽  
Brown Fat ◽  
Fat Cells ◽  
Two Parameters ◽  
Parallel Measurements ◽  
Thermogenic Capacity

The maximum thermogenic capacity of brown fat cells from control and cold acclimated rats was measured using a continuous-flow microcalorimetric system, The content of the 32.000 D, brown fat specific protein, thermogenin, was measured in the cells used for heat production measurements by competitive ELISA. The ratio between the maximal thermogenic capacity and the amount ofthermogenin for control and cold acclimated rats was compared. It was found that the ratio between the two parameters decreased during cold acclimation due to a decrease in maximal thermogenic capacity and an increase in the amount ofthermogenin, indicating regulation of heat production either at thermogenin or receptor level.

Effects of P2 purinergic receptor stimulation in brown adipocytes

1997 ◽  
Vol 273 (2) ◽  
pp. C679-C686 ◽  
Author(s):  
S. C. Lee ◽  
P. A. Pappone
Keyword(s):  
Heat Production ◽  
Purinergic Receptor ◽  
Cytosolic Calcium ◽  
Extracellular Atp ◽  
Brown Fat ◽  
Brown Adipocyte ◽  
Fat Cells ◽  
Sympathetic Stimulation ◽  
Adrenergic Stimulation ◽  
Brown Adipocytes

Sympathetic stimulation of brown adipocytes plays a major role in body energy homeostasis by activating energy-wasting pathways. Sympathetic neuronal input initiates a variety of metabolic, developmental, and membrane responses in brown fat cells. Many of these actions are mediated by adrenergic pathways mobilized by released norepinephrine. However, since sympathetic stimulation may also release vesicular ATP, we tested brown fat cells for ATP responses. Micromolar concentrations of extracellular ATP had a number of effects on brown adipocytes. We have shown previously that ATP elicits substantial (average of approximately 30%) increases in cell membrane capacitance (P. A. Pappone and S. C. Lee, J. Gen. Physiol. 108: 393-404, 1996). Here, we show that cytosolic calcium levels were increased by ATP, both through release from intracellular stores and through influx, as assessed by fura 2 imaging. In addition, ATP indirectly activated a nonselective cation conductance that was independent of cytosolic calcium levels in patch voltage-clamped brown fat cells. Similar calcium, conductance, and capacitance responses could be activated by 2-methylthio-ATP and ADP, consistent with mediation by a P2 type purinergic receptor. Calorimetric measurements from cell suspensions showed that ATP increased basal heat production of isolated brown fat cells by approximately 40% but had no effect on the greater than fivefold increase in heat production seen with maximal adrenergic stimulation. These myriad responses to extracellular ATP suggest that P2 receptor-mediated signaling is important in brown adipocyte physiology and that sympathetic stimulation may normally activate purinergic as well as adrenergic pathways in brown fat.

Cold-induced developmental changes in fat cell size and number in brown adipose tissue of the rat

1981 ◽  
Vol 240 (4) ◽  
pp. E379-E383 ◽  
Author(s):  
C. Senault ◽  
G. Cherqui ◽  
M. Cadot ◽  
R. Portet
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Cold Acclimation ◽  
Cell Size ◽  
Brown Fat ◽  
Control Group ◽  
Fat Cells ◽  
Fat Cell ◽  
Brown Adipose ◽  
The Mean

Seven-week-old Long-Evans rats were acclimated to a constant temperature of either 28 degrees C (control group) or 5 degrees C (cold-acclimated group). Cold acclimation induced a 70% increase in the interscapular brown adipose tissue (IBAT) relative mass, a 35% increase in DNA content, and a 44% decrease in triglyceride (TG) content, which resulted in a 51% decrease of the TG/DNA ratio. A procedure is described by which brown fat cells were isolated, with a yield of 21% from the IBAT of the control group and of 38% in the cold-acclimated group. In both groups, the brown fat cells accounted for 35-37% of the total cells in the tissue. Cold acclimation induced decreases in the mean fat cell diameter (about 20%), the mean fat cell TG content (50%), and the fat cell TG/DNA ratio (50%). The total number of IBAT fat cells was significantly increased in cold-acclimated rats. It is concluded that cold acclimation involves a hyperplasia of the IBAT, associated with a decrease of fat cell size without any alteration of the fat cell-to-nonfat cell ratio.

scholarly journals Cold-induced reduction in Giα proteins in brown adipose tissue. Effects on the cellular hypersensitization to noradrenaline caused by pertussis-toxin treatment

1996 ◽  
Vol 314 (3) ◽  
pp. 761-768 ◽  
Author(s):  
Petr SVOBODA ◽  
Lena UNELIUS ◽  
Andrea DICKER ◽  
Barbara CANNON ◽  
Graeme MILLIGAN ◽  
...  
Keyword(s):  
Cold Acclimation ◽  
Pertussis Toxin ◽  
Fold Increase ◽  
Brown Fat ◽  
Fat Cells ◽  
Brown Adipose ◽  
Increased Sensitivity ◽  
Gi Proteins ◽  
Thermogenic Response ◽  
In Cells

The significance of Gi proteins for the physiological desensitization phenomena observed in brown-fat cells from cold-acclimated hamsters was investigated. For this purpose, pertussis toxin (the inhibitor of Gi function) was injected into control and cold-acclimated hamsters. After 3 days the thermogenic response to noradrenaline injection was monitored in the intact animals. It was found that the pertussis-toxin pretreatment did not affect the thermogenic response to noradrenaline. Nonetheless, the pertussis toxin pretreatment had a dramatic effect on the noradrenaline-sensitivity of isolated brown-fat cells (measured the following day as the respiratory response): a 250-fold-increased sensitivity to noradrenaline was observed in cells from control animals that had been pertussis-toxin pretreated. However, only a 20-fold increase was observed in cells from cold-acclimated hamsters, implying a lower complement of the Gi system in these cells. Therefore the content of Gi proteins was determined by quantitative immunoblotting of purified plasma-membrane proteins. Cold acclimation resulted in a nearly 50% reduction in the content of Gi1α and Gi2α, as well as of the β-subunit, both when expressed on a protein basis and when related to the content of forskolin-stimulated adenylyl cyclase; when expressed per unit of [3H]ouabain-binding (Na+/K+-ATPase), the reduction was even higher. In view of the magnitude of the pertussis-toxin effect, it was concluded that Gi proteins must play a substantial role in the regulation of the response of brown-fat cells to noradrenaline. As the capacity of the Gi pathway is reduced rather than augmented during cold acclimation, Gi activity cannot be responsible for the desensitization to noradrenaline observed in cells from cold-acclimated animals. However, the reduced Gi content may explain the earlier observed desensitization to adenosine that occurs after acclimation to cold.

scholarly journals The Isolation and Metabolism of Brown Fat Cells

1967 ◽  
Vol 242 (8) ◽  
pp. 1887-1894 ◽  
Author(s):  
John N. Fain ◽  
Nora Reed ◽  
Richard Saperstein
Keyword(s):  
Brown Fat ◽  
Fat Cells

Metabolic control in isolated brown fat cells

Lipids ◽  
1970 ◽  
Vol 5 (2) ◽  
pp. 204-209 ◽  
Author(s):  
Olov Lindberg ◽  
Stanley B. Prusiner ◽  
Barbara Cannon ◽  
Te May Ching ◽  
R. H. Eisenhardt
Keyword(s):  
Metabolic Control ◽  
Brown Fat ◽  
Fat Cells

Hyperprolactinemia prevents short photoperiod-induced changes in brown fat

1989 ◽  
Vol 256 (1) ◽  
pp. R174-R180
Author(s):  
K. S. Kott ◽  
B. J. Moore ◽  
L. Fournier ◽  
B. A. Horwitz
Keyword(s):  
Protein Content ◽  
Fat Mass ◽  
Carcass Composition ◽  
Brown Fat ◽  
Short Photoperiod ◽  
Necessary Condition ◽  
Tissue Mass ◽  
The Right ◽  
Induced Changes ◽  
Thermogenic Capacity

Previous studies demonstrated that short photoperiod exposure significantly decreases circulating prolactin levels. The present study investigated the possibility that concomitant changes in brown fat tissue mass, protein content, thermogenic capacity, and carcass composition are dependent on this change in prolactin levels. Male golden (Syrian) hamsters were sham operated and exposed to a short (10L:14D) or long (14L:10D) photoperiod. A third group was implanted with exogenous pituitaries under the right kidney capsule and exposed to a short photoperiod. In experiment I, 4 wk of short- vs. long-photoperiod exposure did not result in significant changes in circulating prolactin levels, nor was there an increase in brown fat mass, protein content, or thermogenic capacity. Four weeks of short-photoperiod exposure did significantly increase carcass lipid content. However, this increase did not occur in hamsters exposed to 4 wk of short photoperiod but made hyperprolactinemic (implanted with two exogenous pituitaries). Ten weeks of short photoperiod significantly reduced circulating prolactin levels. Concomitantly, brown fat mass, protein content, and thermogenic capacity, as well as carcass fat, were increased. These short-photoperiod-induced changes were not observed in similarly exposed hamsters that were made hyperprolactinemic via two implanted pituitaries. In experiment II, similar changes in brown fat and body composition occurred in sham-operated hamsters exposed to 10 wk of short photoperiod. These changes were prevented in hamsters exposed to 10 wk of short photoperiod but made hyperprolactinemic via only one implanted pituitary. These results suggest that decreased prolactin is a necessary condition for the increased brown fat mass, protein content, and thermogenic capacity that occurs when golden hamsters are exposed to short photoperiod.

Adrenergic modulation of intracellular pH in isolated brown fat cells from hamster and rat

1994 ◽  
Vol 267 (2) ◽  
pp. C349-C356 ◽  
Author(s):  
S. C. Lee ◽  
J. S. Hamilton ◽  
T. Trammell ◽  
B. A. Horwitz ◽  
P. A. Pappone
Keyword(s):  
Intracellular Ph ◽  
Uncoupling Protein ◽  
Cell Types ◽  
Brown Fat ◽  
Neonatal Rat ◽  
Fat Cells ◽  
Adrenergic Stimulation ◽  
Regulatory Systems ◽  
Ratio Imaging ◽  
Free Media

The activity of the uncoupling protein in brown fat mitochondria is enhanced at alkaline pH, leading to the hypothesis that changes in intracellular pH (pHi) may modulate the thermogenic response to sympathetic stimulation. We employed ratio imaging of the fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein to measure pHi in acutely isolated single brown fat cells from hamster and neonatal rat and in cultured rat cells. Basal pHi averaged approximately 7.2 in HCO3- media and 0.1-0.15 pH units lower in nominally HCO3(-)-free media in all cell types. In both HCO3- and HCO3(-)-free media, stimulation with norepinephrine (NE) typically caused an alkalinization of approximately 0.05-0.1 pH units, which was followed by a smaller net acidification occurring primarily after NE was removed. Alkalinization seemed to be mediated predominantly by alpha-adrenergic stimulation, while acidification most often followed beta-adrenergic activation. Similar pHi changes were elicited by NE in rat and hamster cells, but responses were more frequent in hamster cells. Assays of recovery from ammonium prepulse-induced acid loads indicated that rat and hamster cells have both Na(+)-H+ and Na(+)- and HCO3(-)-dependent regulatory systems, while hamster cells have, in addition, a Na(+)-independent recovery mechanism activated at acid pHi. We conclude that alpha-adrenergic alkalinization of brown fat may contribute to the control of thermogenesis.

scholarly journals Membrane responses to norepinephrine in cultured brown fat cells.

1990 ◽  
Vol 95 (3) ◽  
pp. 523-544 ◽  
Author(s):  
M T Lucero ◽  
P A Pappone
Keyword(s):  
Brown Fat ◽  
Fat Cells ◽  
Adrenergic Agonists ◽  
Whole Cell ◽  
K Channels ◽  
Inward Current ◽  
General Physiology ◽  
Perforated Patch ◽  
Beta Adrenergic Agonists ◽  
Outward Currents

We used the "perforated-patch" technique (Horn, R., and A. Marty, 1988. Journal of General Physiology. 92:145-159) to examine the effects of adrenergic agonists on the membrane potentials and membrane currents in isolated cultured brown fat cells from neonatal rats. In contrast to our previous results using traditional whole-cell patch clamp, 1-23-d cultured brown fat cells clamped with the perforated patch consistently showed vigorous membrane responses to both alpha- and beta-adrenergic agonists, suggesting that cytoplasmic components essential for the thermogenic response are lost in whole-cell experiments. The membrane responses to adrenergic stimulation varied from cell to cell but were consistent for a given cell. Responses to bath-applied norepinephrine in voltage-clamped cells had three possible components: (a) a fast transient inward current, (b) a slower outward current carried by K+ that often oscillated in amplitude, and (c) a sustained inward current largely by Na+. The fast inward and outward currents were activated by alpha-adrenergic agonists while the slow inward current was mediated by beta-adrenergic agonists. Oscillating outward currents were the most frequently seen response to norepinephrine stimulation. Activation of this current, termed IK,NE, was independent of voltage and seemed to be carried by Ca2(+)-activated K channels since the current oscillated in amplitude at constant membrane potential and gradually decreased when the cells were bathed with calcium-free external solution. IK,NE had a novel pharmacology in that it could be blocked by 4-aminopyridine, tetraethylammonium, apamin, and charybdotoxin. Both IK,NE and the voltage-gated K channels also present in brown fat (Lucero, M. T., and P. A. Pappone, 1989a. Journal of General Physiology. 93:451-472) may play a role in maintaining cellular homeostasis in the face of the high metabolic activity involved in thermogenesis.

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