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  • 1
    Electronic Resource
    Electronic Resource
    Dissociation between brown adipose tissue thermogenesis and sympathetic activity in rats with high plasma levels of oestradiol (1994)
    Springer
    Pflügers Archiv 426 (1994), S. 40-43 
    Details
    ISSN: 1432-2013
    Keywords: Brown adipose tissue ; Cold-acclimation ; Noradrenaline turnover ; Oestradiol ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It has been shown previously that high plasma levels of oestradiol inhibit brown adipose tissue thermogenesis. Since rats and mice show a close association between thermogenic activity in and sympathetic discharge to brown fat, we measured the noradrenaline turnover in rats with high plasma levels of oestradiol to establish whether the observed inhibition of thermogenic activity is brought about by a reduction in the sympathetic drive to brown adipocytes. Oestradiol-filled Silastic capsules were implanted subcutaneously in female rats previously acclimated either to thermoneutrality or to cold. Control rats received empty implants. After 15 days treatment, noradrenaline turnover was measured by blocking its synthesis with α-methyl-p-tyrosine. As expected, noradrenaline turnover was higher in cold-acclimated rats than in rats kept at thermoneutrality. The presence of high plasma oestradiol levels did not alter sympathetic activity in any of the treated groups despite reducing thermogenic activity. This result reveals that oestradiol dissociates the thermogenic activity of brown adipose tissue from its sympathetic activation. Such dissociation has never been previously reported in rats, although it seems to be common in Syrian hamsters. However the causative factor in this species is unknown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374668
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Oxygen consumption of oestradiol-treated rats (1994)
    Springer
    Pflügers Archiv 426 (1994), S. 351-353 
    Details
    ISSN: 1432-2013
    Keywords: Rat ; Brown adipose tissue ; Noradrenaline responsiveness ; Oxygen consumption ; Cold acclimation ; Body temperature ; Oxidative capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rectal temperature and oxygen consumption (üüO2) were monitored in female rats acclimated either to cold or to thermoneutrality and with and without chronic administration of oestradiol. The hormone is known to inactivate brown adipose tissue (BAT) and to reduce its response to noradrenaline (NA). The role of sympathetic control was studied by administering NA or the adrenergic blocker propranolol. Oestradiol treatment did not affect rectal temperature in the states of acclimation to thermoneutrality and to cold, nor did it change the hypothermic response of cold-exposed rats to temporary food deprivation. In the cold-acclimated rats, both controls and oestradiol-treated animals exhibited similar degrees of metabolic reduction after propranolol administration in the cold and similar degrees of metabolic activation by NA at thermoneutrality. Rats acclimated to thermoneutrality showed a larger metabolic response to NA when treated with oestradiol. The results suggest that oestradiol, while inactivating the BAT response to NA, activates the NA responsiveness of other metabolically active tissues in cold-induced thermogenesis. The observation of a greater oxidative capacity in the kidney and the rectus abdominis muscle of oestradiol-treated, cold-acclimated rats would be in line with this proposal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374793
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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