Urinary Excretion of Cyclic AMP by Cold-Acclimated Rats

1974 ◽  
Vol 52 (5) ◽  
pp. 414-417 ◽  
Author(s):  
Michelle Muirhead ◽  
Aileen Inglis ◽  
Jean Himms-Hagen
Keyword(s):  
Cyclic Amp ◽  
Metabolic Rate ◽  
Room Temperature ◽  
Metabolic Response ◽  
Adenyl Cyclase ◽  
Nonshivering Thermogenesis ◽  
Brown Adipose ◽  
Adenyl Cyclase System ◽  
First Time ◽  
Noradrenaline And Adrenaline

Cold-acclimated rats living in the cold (4°) excrete more cyclic AMP in their urine than do control warm-acclimated rats living at room temperature (26°–28°). However, cold-acclimated rats, returned to the cold after a few days at room temperature and presumably raising their metabolic rate by nonshivering thermogenesis in response to the noradrenaline and adrenaline secreted by the sympathetic nervous system, excrete the same amount of cyclic AMP in their urine as do warm-acclimated rats of the same age put into the cold for the first time and presumably raising their metabolic rate by shivering. Thus, no evidence could be found for an altered utilization of the adenyl cyclase system in the cold-acclimated rat. This, together with previous findings of unaltered levels and properties of noradrenaline-stimulated adenyl cyclase in brown adipose tissue and skeletal muscle of cold-acclimated rats, leads us to the conclusion that the enhancement of the metabolic response to noradrenaline in cold-acclimated rats is not due to any alteration in the adenyl cyclase system.

Changes in the Adenyl Cyclase System of Skeletal Muscle of Cold-Acclimated Rats

1974 ◽  
Vol 52 (3) ◽  
pp. 176-180 ◽  
Author(s):  
Michelle Muirhead ◽  
Jean Himms-Hagen
Keyword(s):  
Skeletal Muscle ◽  
Plasma Membrane ◽  
Cold Acclimation ◽  
Metabolic Response ◽  
Adenyl Cyclase ◽  
Nonshivering Thermogenesis ◽  
Receptor System ◽  
Adenyl Cyclase System ◽  
Shivering Thermogenesis ◽  
Stimulation Of

No change could be detected in the adenyl cylase system (basal activity, noradrenaline-stimulated activity, adrenaline-stimulated activity, fluoride-stimulated activity) of skeletal muscle of cold-acclimated rats. It is concluded that the enhancement of metabolic response to noradrenaline during cold-acclimation, which occurs principally in skeletal muscle, can not be attributed to an alteration in this component of the receptor system for noradrenaline.An increase in the activity of the catecholamine-stimulated and fluoride-stimulated adenyl cyclase of skeletal muscle occurs during the 1st week of exposure to cold and has disappeared by the time the rats are fully acclimated. This increase coincides with the period of shivering thermogenesis rather than with the development of nonshivering thermogenesis; it may be related to the intense and repeated stimulation of plasma membrane associated with shivering.

Dependence of Platelet Adenyl Cyclase System on Oxidative Phosphorylation

1975 ◽  
Vol 34 (01) ◽  
pp. 042-049 ◽  
Author(s):  
Shuichi Hashimoto ◽  
Sachiko Shibata ◽  
Bokro Kobayashi
Keyword(s):  
Cyclic Amp ◽  
Oxidative Phosphorylation ◽  
Sodium Succinate ◽  
Potassium Cyanide ◽  
Adenyl Cyclase ◽  
Mitochondrial Oxidative Phosphorylation ◽  
Adenyl Cyclase Activity ◽  
Intact Rabbit ◽  
Adenyl Cyclase System ◽  
Cyclic Amp Synthesis

SummaryThe radioactive adenosine 3′,5′-monophosphate (cyclic AMP) level derived from 8-14C adenine in intact rabbit platelets decreased in the presence of mitochondrial inhibitor (potassium cyanide) or uncoupler (sodium azide), and markedly increased by the addition of NaF, monoiodoacetic acid (MIA), or 2-deoxy-D-glucose. The stimulative effect of the glycolytic inhibitors was distinctly enhanced by the simultaneous addition of sodium succinate. MIA did neither directly stimulate the adenyl cyclase activity nor inhibit the phosphodiesterase activity. These results suggest that cyclic AMP synthesis in platelets is closely linked to mitochondrial oxidative phosphorylation.

Cold acclimation-recruited nonshivering thermogenesis: the Syrian hamster is not an exception

1995 ◽  
Vol 269 (4) ◽  
pp. R767-R774 ◽  
Author(s):  
A. Dicker ◽  
B. Cannon ◽  
J. Nedergaard
Keyword(s):  
Metabolic Rate ◽  
Cold Acclimation ◽  
Resting Metabolic Rate ◽  
High Rate ◽  
In Vivo Studies ◽  
Nonshivering Thermogenesis ◽  
Brown Adipose ◽  
Thermogenic Response

Biochemical evidence from in vitro studies of brown adipose tissue in Syrian hamsters indicates a significant degree of recruitment of the tissue as an effect of cold acclimation. However, earlier in vivo studies indicate a lack of recruitment of nonshivering thermogenesis in the intact animal as a result of cold acclimation. Because of this apparent discrepancy, the occurrence of cold acclimation-recruited nonshivering thermogenesis in hamsters was investigated. Hamsters were cold acclimated to 6 degrees C or remained at 24 degrees C (controls), and their thermogenic response was investigated in an open-circuit system at 24 degrees C. Cold acclimation resulted in a small increase in resting metabolic rate and a major increase in the thermogenic response to norepinephrine (61% increase over resting metabolic rate in controls and 156% increase in cold-acclimated animals). The absolute beta 3-specific adrenergic agonist CGP-12177 also induced a high rate of nonshivering thermogenesis, which was similarly recruited. It was concluded that, concerning the relative effect of recruitment on the capacity for nonshivering thermogenesis, the intact hamsters responded as would be predicted from in vitro experiments. Thus the hamster does not seem to constitute an exception to the general patterns described for other rodents concerning recruitment of nonshivering thermogenesis due to cold acclimation.

Norepinephrine thermogenesis in seasonally acclimatized and cold acclimated red-backed voles in Alaska

1976 ◽  
Vol 54 (2) ◽  
pp. 146-153 ◽  
Author(s):  
Dale D. Feist ◽  
Mario Rosenmann
Keyword(s):  
Metabolic Rate ◽  
Small Mammal ◽  
Cold Exposure ◽  
Metabolic Response ◽  
Nonshivering Thermogenesis ◽  
Metabolic Capacity ◽  
Mammal Species ◽  
Winter Peak ◽  
Clethrionomys Rutilus ◽  
Small Mammal Species

The calorigenic response (millilitres O2 per gram per hour) to injected norepinephrine (NE) was compared as an index of nonshivering thermogenesis (NST) in the following groups of the Alaskan red-backed vole (Clethrionomys rutilus): (1) summer, (2) fall acclimatized, (3) winter acclimatized, (4) 20 °C acclimated and (5) 5 °C acclimated. The metabolic response was tested at thermoneutrality (25 °C) and during cold exposure (5 °C).Winter acclimatized voles showed a significantly greater metabolic response to NE than summer voles at both 25 °C and 5 °C. In summer or winter voles the total metabolic rate after NE (MNE) was similar at 25 °C and 5 °C but the fraction of the total caused by exogenous NE was lower at 5 °C. Thus, thermogenesis during cold exposure and resulting from exogenous NE appear to be based on the same mechanism, and NE has thermoregulatory significance in these voles. The magnitude of the NE response in winter voles was comparable to the highest values reported for bats and exceeded levels reported for other adult small mammal species. Summer acclimatized voles and those acclimated to 20 °C in the laboratory were comparable in their response to NE but winter acclimatized voles were significantly more sensitive to NE than voles acclimated to 5 °C. The seasonal winter peak in MNE coincided with peaks previously found for maximum metabolic capacity (Mmax), maximum brown fat, and the period of coldest temperatures in December–January. The ratio of MNE to Mmax was similar throughout the year. The results suggest that small arctic–subarctic rodents have a greater capacity for NE stimulated NST than rodents from temperate latitudes probably because they are acclimatized to colder seasonal conditions.

The effect of environmental temperature during pregnancy on thermoregulation in the newborn lamb

1985 ◽  
Vol 41 (3) ◽  
pp. 341-347 ◽  
Author(s):  
A. W. Stott ◽  
J. Slee
Keyword(s):  
Blood Glucose ◽  
Metabolic Rate ◽  
Metabolic Response ◽  
Water Immersion ◽  
Cold Treatment ◽  
Rate Capability ◽  
Late Pregnancy ◽  
Cold Test ◽  
Brown Adipose ◽  
Shivering Thermogenesis

AbstractTwenty-four pregnant Scottish Blackface ewes were divided into three temperature-treatment groups 14 days before expected lambing: closely shorn and kept at 6°C (cold treatment, CD); in full fleece at 26°C (warm treatment, WM); and in full fleece at 6°C (controls, CL). Food allocation and intakes were similar for each group. Their lambs were tested for cold-induced summit metabolic rate capability (SMR) on the day of birth at a mean age of 12 h using water immersion to provide cooling. On the following day, the calorigenic response to subcutaneous injections of noradrenaline (NA) was measured to assess non-shivering thermogenesis capability. The ewes were blood-sampled during pregnancy and the lambs before and after the SMR test.In the ewes, blood glucose and free fatty acid levels were higher during cold treatment, but not significantly so. Blood glucose was lower in lambs from CD ewes (CD lambs) before SMR tests; other differences were not significant.During the cold test, SMR was highest in CD lambs, but not significantly so. Rectal temperature declined least during test in the CD lambs (P < 0·05).The peak metabolic response (PMR) following NA injection was about 1·5 times greater in CD lambs than in the CL and WM lambs (P < 0·05). The mean elevation of PMR over thermoneutral metabolic rate was respectively: 2·8, 1·8 and 1·7 times in the CD, CL and WM lambs (P < 0·05), and this elevation was sustained for longer in the CD lambs (P < 0·01). Thus, the total metabolic response to NA was markedly greater in CD lambs.It was concluded that cold exposure during late pregnancy favoured the deposition of (or checked the normal decline in) foetal brown adipose tissue, so raising the neonatal capacity for non-shivering thermogenesis.

Potentiated muscular thermogenesis in cold-acclimated muscovy duckling

1985 ◽  
Vol 249 (5) ◽  
pp. R533-R538 ◽  
Author(s):  
H. Barre ◽  
A. Geloen ◽  
J. Chatonnet ◽  
A. Dittmar ◽  
J. L. Rouanet
Keyword(s):  
Metabolic Rate ◽  
Muscular Activity ◽  
Threshold Temperature ◽  
Emg Activity ◽  
Nonshivering Thermogenesis ◽  
Brown Adipose ◽  
Lower Critical Temperature ◽  
Cold Shivering ◽  
Two Temperatures ◽  
Extreme Cold

The capacity for nonshivering thermogenesis (NST) was examined in 26- to 27-day cold-acclimated (CA) muscovy ducklings reared for 21 days at 4 degrees C. Metabolic rate and integrated electromyographic (EMG) muscle activity were measured at ambient temperature ranging from -10 to 28 degrees C. Compared with controls reared at 30 degrees C, CA ducklings were more resistant to cold and had higher peak metabolic rate in extreme cold. Shivering threshold temperature of CA ducklings was 14.2 degrees C lower than lower critical temperature, whereas for controls the two temperatures were similar. Thus CA ducklings exhibited an NST in moderate cold. In addition, at temperatures that produced shivering, EMG activity in CA duckling muscle was lesser than that of controls, even at a higher metabolic rate. Because these ducklings are devoid of brown adipose tissue, these results indicated an increased thermogenic efficiency of muscular activity in CA ducklings.

Isoproterenol-induced blood flow in rats acclimated to room temperature and cold

1984 ◽  
Vol 246 (5) ◽  
pp. R747-R752
Author(s):  
S. J. Wickler ◽  
B. A. Horwitz ◽  
S. F. Flaim ◽  
K. F. LaNoue
Keyword(s):  
Blood Flow ◽  
Room Temperature ◽  
Metabolic Response ◽  
Fold Increase ◽  
Brown Fat ◽  
Beta Agonist ◽  
Nonshivering Thermogenesis ◽  
Blood Flows ◽  
White Fat ◽  
Isoproterenol Infusion

Blood flow was measured with labeled microspheres in cold (6 degrees C)- and room-temperature-acclimated rats at rest and during infusion of the beta-agonist, isoproterenol. Isoproterenol elicited decreased mass-specific blood flows (ml . g-1 . min-1) to liver (55% of control), kidney (48%), and white fat (64%) in room-temperature-acclimated (RT) rats. Blood flow was similarly decreased in liver (51%), kidney (37%), and white fat (70%) in cold-acclimated (CA) rats. In contrast, isoproterenol increased blood flows to brown fat and cardiac and skeletal muscles. The blood flows to cardiac muscle during isoproterenol infusion were comparable in both RT (12.7 ml . g-1 . min-1) and CA (11.7 ml . g-1 . min-1) animals, representing increases of 2.9- and 2.6-fold above control values, respectively. Blood flow to skeletal muscle was also similarly elevated in RT and CA animals, representing increases 5.9 and 5.6 times those of their respective control values. In contrast, although isoproterenol greatly stimulated (ca. 8-fold) blood flow to brown fat (interscapular plus cervical depots) in RT animals, it had a greater effect on these two depots in the CA rats (18-fold increase). These data emphasize the importance of brown fat as a major effector of nonshivering thermogenesis as well as the importance of beta-adrenergic receptors in mediating the metabolic response of nonshivering thermogenesis.

The molecular and biochemical basis of nonshivering thermogenesis in an African endemic mammal, Elephantulus myurus

2007 ◽  
Vol 293 (5) ◽  
pp. R2120-R2127 ◽  
Author(s):  
Nomakwezi Mzilikazi ◽  
Martin Jastroch ◽  
Carola W. Meyer ◽  
Martin Klingenspor
Keyword(s):  
Cold Acclimation ◽  
Metabolic Response ◽  
Uncoupling Protein ◽  
Mammalian Species ◽  
Liver Mitochondria ◽  
Nonshivering Thermogenesis ◽  
Vertebrate Lineage ◽  
Biochemical Basis ◽  
Fat Deposits ◽  
Brown Adipose

Uncoupling protein 1 (UCP1) mediated nonshivering thermogenesis (NST) in brown adipose tissue (BAT) is an important avenue of thermoregulatory heat production in many mammalian species. Until recently, UCP1 was thought to occur exclusively in eutherians. In the light of the recent finding that UCP1 is already present in fish, it is of interest to investigate when UCP1 gained a thermogenic function in the vertebrate lineage. We elucidated the basis of NST in the rock elephant shrew, Elephantulus myurus (Afrotheria: Macroscelidea). We sequenced Ucp1 and detected Ucp1 mRNA and protein restricted to brown fat deposits. We found that cytochrome c oxidase activity was highest in these deposits when compared with liver and skeletal muscle. Consistent with a thermogenic function of UCP1 isolated BAT mitochondria showed increased state 4 respiration in the cold, as well as palmitate-induced, GDP-sensitive proton conductance, which was absent in liver mitochondria. On the whole animal level, evidence of thermogenic function was further corroborated by an increased metabolic response to norepinephrine (NE) injection. Cold acclimation (18°C) led to an increased basal metabolic rate relative to warm acclimation (28°C) in E. myurus, but there was no evidence of additional recruitment of NE-induced NST capacity in response to cold acclimation. In summary, we showed that BAT and functional UCP1 are already present in a member of the Afrotheria, but the seasonal regulation and adaptive value of NST in Afrotherians remain to be elucidated.

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