FATTY ACID METABOLISM DURING NOREPINEPHRINE INDUCED THERMOGENESIS IN THE COLD ACCLIMATIZED RAT
Abstract
The biochemical mechanisms underlying norepinephrine-induced thermo-genesis and the possible relationship of this hormone to nonshivering thermogenesis were investigated in cold-acclimatized rats. An intravenous infusion of 1-nonrepinephrine caused a marked fall in the Respiratory Quotient, indicating a predominance of fat oxidation. Cold-acclimatized animals had higher liver and blood levels of nonesterified fatty acids (NEFA) than control animals, but nonrepinephrine infusions raised blood NEFA to the same level in both groups. Cold acclimatization was associated with an increased capacity to turn over NEFA, as indicated by an elevated capacity for the oxidation of NEFA in the liver tissue and increased sensitivity of epididymal fat to a norepinephrine-induced release of NEFA. Continuous measurements of respiratory gas exchange during acute cold exposure (5 and -15 C) showed the Respiratory Quotient to be reduced only during the transition stage from a lower to a higher metabolic steady state. Norepinephrine is not the sole mediator of non-shivering thermogenesis. Rather, it probably acts through a stimulation of NEFA metabolism to rapidly inincrease the heat production. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1962
- Accession Number
- AD0285014
Entities
People
- Anna M. Larson
- John P. Hannon