Abstract
In young adult laboratory rats exposed to cold (6°C) the brown adipose tissue undergoes time-dependent increases in cellularity, vascular supply, and total mass. These changes are largely complete after 16 days in the cold and concurrent generally with the development of a thermoregulatory state not greatly dependent upon shivering. Histologically the brown fat changes from a tissue having both unilocular and multilocular fat cell types to one having almost exclusively the latter. During the first 6 to 12 hours in cold, the multilocular cells lose their lipid vacuoles and decrease in size, but these features are restored to normal by 24 hours. Cell proliferation, as estimated by the DNA synthetic index method (using tritiated thymidine autoradiography), appears in the reticuloendothelial cells of the brown fat at 1 day of cold exposure, becomes maximal at 4 days, and returns to the control level by 16 days. In animals injected with tritiated thymidine on the 3rd day of cold exposure and then maintained for 1 or more additional days in the cold, autoradiographs indicate that new brown fat (multilocular) cells arise by cytogenesis from reticuloendothelial progenitor cells and not by proliferation of existing brown fat cells. Throughout this and subsequent periods, cells of the epididymal white adipose tissue slowly decrease in size. Because a thermogenic role in cold acclimation has been established for the brown fat, the reported changes are regarded as adaptive responses to a cold environment.
Full Text
The Full Text of this article is available as a PDF (1.2 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- CAMERON I. L., GREULICH R. C. Evidence for an essentially constant duration of DNA synthesis in renewing epithelia of the adult mouse. J Cell Biol. 1963 Jul;18:31–40. doi: 10.1083/jcb.18.1.31. [DOI] [PMC free article] [PubMed] [Google Scholar]
- CAMERON I. L. IS THE DURATION OF DNA SYNTHESIS IN SOMATIC CELLS OF MAMMALS AND BIRDS A CONSTANT? J Cell Biol. 1964 Jan;20:185–188. [PMC free article] [PubMed] [Google Scholar]
- MESSIER B., LEBLOND C. P. Preparation of coated radioautographs by dipping sections in fluid emulsion. Proc Soc Exp Biol Med. 1957 Oct;96(1):7–10. doi: 10.3181/00379727-96-23380. [DOI] [PubMed] [Google Scholar]
- SELYE H., TIMIRAS P. S. Participation of brown fat tissue in the alarm reaction. Nature. 1949 Oct 29;164(4174):745–745. doi: 10.1038/164745b0. [DOI] [PubMed] [Google Scholar]
- SMALLEY R. L., DRYER R. L. Brown fat: thermogenic effect during arousal from hibernation in the bat. Science. 1963 Jun 21;140(3573):1333–1334. doi: 10.1126/science.140.3573.1333. [DOI] [PubMed] [Google Scholar]
- SMITH R. E., HOCK R. J. Brown fat: thermogenic effector of arousal in hibernators. Science. 1963 Apr 12;140(3563):199–200. doi: 10.1126/science.140.3563.199. [DOI] [PubMed] [Google Scholar]
- SMITH R. E., HOIJER D. J. Metabolism and cellular function in cold acclimation. Physiol Rev. 1962 Jan;42:60–142. doi: 10.1152/physrev.1962.42.1.60. [DOI] [PubMed] [Google Scholar]
- SMITH R. E., ROBERTS J. C. THERMOGENESIS OF BROWN ADIPOSE TISSUE IN COLD-ACCLIMATED RATS. Am J Physiol. 1964 Jan;206:143–148. doi: 10.1152/ajplegacy.1964.206.1.143. [DOI] [PubMed] [Google Scholar]