Summary
It has been shown that the same modifications on the composition of brown adipose
tissue (BAT) which are normally induced following cold stimulation are also observed
in hypophysectomized rats acclimated either at 28° C or 15° C. To test the possibility
of BAT stimulation in hypophysectomized rats, we have determined some enzymatic activities
known to modulate the energy supply to that organ. Seven week old Long-Evans rats
were hypophysectomized. Three weeks later, they were exposed to either 28° C or 15°
C ambient temperature for five or six weeks. Hypophysectomized rats were compared
to age matched or weight matched controls. Total lipoprotein lipase activity (LPL)
(triglyceride uptake) was enhanced in BAT of 28° C hypophysectomized rats compared
to controls. Cold acclimation led to a large increased activity. Total LPL activity
was comparable in BAT of hypophysectomized and control rats. Total malic enzyme and
glucose-6-phosphate dehydrogenase activities (in situ lipogenesis) were doubled in
BAT of 28° C hypophysectomized compared to controls. A large enhancement was observed
in BAT of either 15° C control or 15° C hypophysectomized rats. Among the studied
organs (liver, white adipose tissue, heart, BAT) hypophysectomy promotes the three
enzyme activities only in BAT. These variations were discussed with relation to the
effect of hypophysectomy on brown adipose tissue at 15° C and 28° C.
Key-Words:
Brown Adipose Tissue
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White Adipose Tissue
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Liver
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Heart
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Lipoprotein Lipase
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Malic Enzyme
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Glucose-6-Phosphate Dehydrogenase
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Hypophysectomy
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Cold Acclimation
