Natural Decreasing Temperature and Photoperiod Conditions or Acute Cold Exposure Affect Circulating Thyroid Hormones, Serum Cholesterol and Type Ii 5'-deiodinase in Brown Adipose Tissue in the Trumpet-tailed Rat, Octodon Degus
Year: 1989
Type: article
Abstract: Adult male degus (Ocrodon degus) were housed in a controlled temperature (22i2°C) and lighting (l4: l0 LD; lights on 07 O0) environment or were placed in a sheltered shed at 32.26°N and 99.43°W which provided access to natural fluctuating photoperiodic and temperature conditions during the months of October and November.Animals maintained under natural autumnal conditions had higher circulating concentrations of triiodothyronine (T3) and cholesterol.Free T3 index (FT3I) was also elevated in these outdoor animals but neither thyroxine (T4), FT,,I nor serum triglycerides were elevated.In the second experiment, adult female degus were exposed to controlled lighting (14:10 LD) but varied (22°C or 8°C) temperatures for 21 h.T3 and FT3I were significantly elevated in animals exposed to cold.T4, FT41, cholesterol and triglycerides were not affected by cold.Type II 5 'deiodinase activity in brown adipose tissue was elevated in cold-exposed degus but no changes in enzyme activity were observed in frontal cerebral cortex, olfactory bulbs nor anterior pituitary.These results suggest that the maintenance of euthermia by nonshivering thermogenesis is one likely mechanism used by the degu to cope with cold.Further, it would appear from previously published results in many species and now including the degu that cholesterol levels are elevated in chronically cold-exposed animals.
Source: Biomedical Research
Language: English
Subfield: Physiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2169028335