Abstract
We previously showed that, although cold-induced thermoregulation is attenuated in 26-mo-old male Fischer 344 (F344) rats, not all rats this age exhibit the same degree of cold-exposed hypothermia or diminished brown adipose tissue nonshivering thermogenic capacity. Examination of this heterogeneity suggested the hypothesis that it was associated with a difference in the physiological state between aged rats that were maintaining stable body weight versus those showing the rapid weight loss often occurring near the end of the rat's natural life span. To test this, we acutely exposed male F344 rats to cold (4 h at 6°C) beginning at 24 mo of age. This exposure was weekly for the first 2 wk and then on alternate weeks as long as the rat's body weight was stable. If body weight progressively declined for 3-5 consecutive days, the rat's response to the acute cold exposure was again measured, as was that of two additional rats not displaying this rapid loss in body weight. If body temperature decreased during the cold exposure to intraperitoneal temperatures ≤32.5°C, the rat was killed with pentobarbital sodium and interscapular brown adipose tissue was removed. One of the age- matched controls was also killed at this time. The age at which body weight showed a spontaneous rapid decline ranged from 24.5 to 29 mos. All eight rats displaying spontaneous rapid weight loss had significant hypothermia during the acute cold exposure, whereas none of the eight weight-stable rats did. The development of hypothermia in the spontaneous rapid weight loss group was not, in general, observed before their weight loss. The weight loss and hypothermia were associated with lower levels of brown fat uncoupling protein and significant changes in body fat and protein. These data suggest that the development of senescence-related hypothermia occurs rapidly and is not a simple function of chronological age or the median life span of the animals. Furthermore, these data imply that the rate of aging in terms of maintenance of thermoregulatory homeostasis has both a gradual and rapid component, the latter being associated with a different physiological state than the former.
| Original language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Regulatory Integrative and Comparative Physiology |
| Volume | 271 |
| Issue number | 5 40-5 |
| State | Published - Nov 1996 |
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Keywords
- brown adipose tissue
- cold exposure
- Fischer 344 rats
ASJC Scopus subject areas
- Physiology
- Physiology (medical)
Cite this
Relationship between cold-induced thermoregulation and spontaneous rapid body weight loss of aging F344 rats. / Mcdonald, Roger B.; Florez-Duquet, Maria; Murtagh-Mark, Carol; Horwitz, Barbara A.
In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology, Vol. 271, No. 5 40-5, 11.1996.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Relationship between cold-induced thermoregulation and spontaneous rapid body weight loss of aging F344 rats
AU - Mcdonald, Roger B.
AU - Florez-Duquet, Maria
AU - Murtagh-Mark, Carol
AU - Horwitz, Barbara A
PY - 1996/11
Y1 - 1996/11
N2 - We previously showed that, although cold-induced thermoregulation is attenuated in 26-mo-old male Fischer 344 (F344) rats, not all rats this age exhibit the same degree of cold-exposed hypothermia or diminished brown adipose tissue nonshivering thermogenic capacity. Examination of this heterogeneity suggested the hypothesis that it was associated with a difference in the physiological state between aged rats that were maintaining stable body weight versus those showing the rapid weight loss often occurring near the end of the rat's natural life span. To test this, we acutely exposed male F344 rats to cold (4 h at 6°C) beginning at 24 mo of age. This exposure was weekly for the first 2 wk and then on alternate weeks as long as the rat's body weight was stable. If body weight progressively declined for 3-5 consecutive days, the rat's response to the acute cold exposure was again measured, as was that of two additional rats not displaying this rapid loss in body weight. If body temperature decreased during the cold exposure to intraperitoneal temperatures ≤32.5°C, the rat was killed with pentobarbital sodium and interscapular brown adipose tissue was removed. One of the age- matched controls was also killed at this time. The age at which body weight showed a spontaneous rapid decline ranged from 24.5 to 29 mos. All eight rats displaying spontaneous rapid weight loss had significant hypothermia during the acute cold exposure, whereas none of the eight weight-stable rats did. The development of hypothermia in the spontaneous rapid weight loss group was not, in general, observed before their weight loss. The weight loss and hypothermia were associated with lower levels of brown fat uncoupling protein and significant changes in body fat and protein. These data suggest that the development of senescence-related hypothermia occurs rapidly and is not a simple function of chronological age or the median life span of the animals. Furthermore, these data imply that the rate of aging in terms of maintenance of thermoregulatory homeostasis has both a gradual and rapid component, the latter being associated with a different physiological state than the former.
AB - We previously showed that, although cold-induced thermoregulation is attenuated in 26-mo-old male Fischer 344 (F344) rats, not all rats this age exhibit the same degree of cold-exposed hypothermia or diminished brown adipose tissue nonshivering thermogenic capacity. Examination of this heterogeneity suggested the hypothesis that it was associated with a difference in the physiological state between aged rats that were maintaining stable body weight versus those showing the rapid weight loss often occurring near the end of the rat's natural life span. To test this, we acutely exposed male F344 rats to cold (4 h at 6°C) beginning at 24 mo of age. This exposure was weekly for the first 2 wk and then on alternate weeks as long as the rat's body weight was stable. If body weight progressively declined for 3-5 consecutive days, the rat's response to the acute cold exposure was again measured, as was that of two additional rats not displaying this rapid loss in body weight. If body temperature decreased during the cold exposure to intraperitoneal temperatures ≤32.5°C, the rat was killed with pentobarbital sodium and interscapular brown adipose tissue was removed. One of the age- matched controls was also killed at this time. The age at which body weight showed a spontaneous rapid decline ranged from 24.5 to 29 mos. All eight rats displaying spontaneous rapid weight loss had significant hypothermia during the acute cold exposure, whereas none of the eight weight-stable rats did. The development of hypothermia in the spontaneous rapid weight loss group was not, in general, observed before their weight loss. The weight loss and hypothermia were associated with lower levels of brown fat uncoupling protein and significant changes in body fat and protein. These data suggest that the development of senescence-related hypothermia occurs rapidly and is not a simple function of chronological age or the median life span of the animals. Furthermore, these data imply that the rate of aging in terms of maintenance of thermoregulatory homeostasis has both a gradual and rapid component, the latter being associated with a different physiological state than the former.
KW - brown adipose tissue
KW - cold exposure
KW - Fischer 344 rats
UR - http://www.scopus.com/inward/record.url?scp=0029958492&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0029958492&partnerID=8YFLogxK
M3 - Article
C2 - 8945943
AN - SCOPUS:0029958492
VL - 271
JO - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
JF - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
SN - 1931-857X
IS - 5 40-5
ER -