Thermogenesis of Brown Fat in Hibernation and Cold Adaptation
111
previously emphasized [13, 15], the vascularity and special localization of
the brown fat serves the requirement for localized application of heat to the
spinal cord, aortic arch, the sympathetic chain, and the vital organs of the
thorax.
References
1. BRUCK, K., U. B. WUNNENBERG: Pfliigers Arch. 283, 1 (1965).
2. DAWKINS, M. J. R., and D. HULL: J. PhysioI. 172, 216 (1964).
3. DONHOFFER, Sz., F. SARDY, and Gy. SZEGVARI: Nature 203, 765 (1964).
4. -, and Z. SZELENYI: Acta Physiol. Hung. 28, 349 (1965).
5. HAYWARD, J. S., and E. G. BALL: BioI. Bull. 131, 94 (1966).
6. -, C. P. LYMAN, and C. R. TAYLOR: Ann. N. Y. Acad. Sci. 131,441 (1965).
7. HElM, T., and D. HULL: J. PhysioI. 186, 42 (1966).
8. HULL, D., and M. M. SEGALL: J. PhysioI. 181, 449 (1965).
9. IMAI, Y., B. A. HORWITZ, and R. E. SMITH: Proc. Soc. Exp. BioI. Med. 127,
717 (1968).
10. JANSKY, L.: Fed. Proc. 25, 1297 (1966).
11. JOEL, C.D.: In:RENoLD,A.E., and G.F.CAHILLJr. (Ed.), Handbook of
Physiology, Section 5, Adipose Tissue, p.59. Washington, D. c.: Am.
Physiol. Soc. 1965.
12. SMALLEY, R. L., and R. DRYER: Science 140, 1333 (1963).
13. SMITH, R. E.: Fed. Proc. 21, 221 (1962).
14. -, and R. J. HOCK: Science 140, 199 (1963).
15. -, and]. C. ROBERTS: Am.]. Physiol. 206, 143 (1964).
Discussion
WOODSTOCK:
(1) Why is the brown fat brown, i.e. is the brown color associated with
differences in the respiratory system? (2) Upon chilling in rats, do marked
changes in Q02 occur in non-brown fat similar to those in brown fat?
SMITH:
(1) The color of the brown fat is ascribed largely to the cellular heme pigments
e.g. cytochromes, and hemoglobin in the rich vascular supply to the tissue.
Additionally, there is evidence that flavoproteins and lipoproteins may also
contribute to the color. The apparent color also changes with seasons in
some hibernators, and in the course of cold exposure the light brown color
of the tissue becomes more reddish in appearance. (2) So far as I am aware, no
data are available on the Q02 of white adipose tissue during cold acclimation.
LANGER:
How large is the amount of total mass of brown adipose tissue in the ground
squirrel as a percentage of total body weight and how did you get this figure?
How much weight of brown fat is lost during the course of arousal from hibernation?
HORWITZ:
(1) In the ground squirrels employed in this study, the mass of the brown fat
relative to that of the total body weight averaged near 4.8 %. This value was
obtained by weighing the brown fat excised respectively from individually
111
previously emphasized [13, 15], the vascularity and special localization of
the brown fat serves the requirement for localized application of heat to the
spinal cord, aortic arch, the sympathetic chain, and the vital organs of the
thorax.
References
1. BRUCK, K., U. B. WUNNENBERG: Pfliigers Arch. 283, 1 (1965).
2. DAWKINS, M. J. R., and D. HULL: J. PhysioI. 172, 216 (1964).
3. DONHOFFER, Sz., F. SARDY, and Gy. SZEGVARI: Nature 203, 765 (1964).
4. -, and Z. SZELENYI: Acta Physiol. Hung. 28, 349 (1965).
5. HAYWARD, J. S., and E. G. BALL: BioI. Bull. 131, 94 (1966).
6. -, C. P. LYMAN, and C. R. TAYLOR: Ann. N. Y. Acad. Sci. 131,441 (1965).
7. HElM, T., and D. HULL: J. PhysioI. 186, 42 (1966).
8. HULL, D., and M. M. SEGALL: J. PhysioI. 181, 449 (1965).
9. IMAI, Y., B. A. HORWITZ, and R. E. SMITH: Proc. Soc. Exp. BioI. Med. 127,
717 (1968).
10. JANSKY, L.: Fed. Proc. 25, 1297 (1966).
11. JOEL, C.D.: In:RENoLD,A.E., and G.F.CAHILLJr. (Ed.), Handbook of
Physiology, Section 5, Adipose Tissue, p.59. Washington, D. c.: Am.
Physiol. Soc. 1965.
12. SMALLEY, R. L., and R. DRYER: Science 140, 1333 (1963).
13. SMITH, R. E.: Fed. Proc. 21, 221 (1962).
14. -, and R. J. HOCK: Science 140, 199 (1963).
15. -, and]. C. ROBERTS: Am.]. Physiol. 206, 143 (1964).
Discussion
WOODSTOCK:
(1) Why is the brown fat brown, i.e. is the brown color associated with
differences in the respiratory system? (2) Upon chilling in rats, do marked
changes in Q02 occur in non-brown fat similar to those in brown fat?
SMITH:
(1) The color of the brown fat is ascribed largely to the cellular heme pigments
e.g. cytochromes, and hemoglobin in the rich vascular supply to the tissue.
Additionally, there is evidence that flavoproteins and lipoproteins may also
contribute to the color. The apparent color also changes with seasons in
some hibernators, and in the course of cold exposure the light brown color
of the tissue becomes more reddish in appearance. (2) So far as I am aware, no
data are available on the Q02 of white adipose tissue during cold acclimation.
LANGER:
How large is the amount of total mass of brown adipose tissue in the ground
squirrel as a percentage of total body weight and how did you get this figure?
How much weight of brown fat is lost during the course of arousal from hibernation?
HORWITZ:
(1) In the ground squirrels employed in this study, the mass of the brown fat
relative to that of the total body weight averaged near 4.8 %. This value was
obtained by weighing the brown fat excised respectively from individually