Springer Online Journal Archives 1860-2000
Summary As has been previously shown, non-shivering thermogenesis is the prevailing mechanism of heat production in the newborn guinea pig exposed to a cool environment. In the course of the first two to three weeks of life, non-shivering thermogenesis is reduced and replaced by shivering. In the present study this process has been shown to be linked with morphological and functional alterations in the multilocular adipose tissue. The functional changes have been evidenced by the following experiments: In two groups of guinea pigs, 0–2, and 25 to 42 days of age, respectively, the local temperature and blood flow were measured in the large fat pad located between the scapulae, in addition to gaseous metabolism, electrical activity of the sceletal musculature and colon temperature. In the young animals the rise of O2-consumption as occuring on cold exposure was accompanied by a temperature rise in the fat tissue (absolute and relative to the colon temperature), whereas electrical activity of the musculature remained low. Blood flow of the fat tissue increased at the same time. In the older animals, the temperature difference between the fat tissue and colon remained low but it occurred shivering. The increase of temperature difference and blood flow was reduced or abolished in the young animals by Alderlin, an adrenergic β-receptor blocking agent that has been previously shown to block non-shivering thermogenesis; on the other hand, the blockade of non-shivering thermogenesis caused an onset of shivering. Further, noradrenaline and adrenaline have been shown to increase blood flow of the fat tissue in the young animals. The results indicate. 1. that the brown adipose tissue can be considered an important site of non-shivering thermogenesis in the newborn guinea pig, and 2. that the thermogenic capacity of the brown fat is diminished with increasing age.
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