Unloading does not increase brown-adipose-tissue activity in rat pups.
Our previous study has shown that chronic hindlimb suspension leads to an increase in both the thermogenic capacity and the activity in brown adipose tissue (BAT) of adult rats (Yamashita, H., Ohira, Y., Wakatsuki, T., Yamamoto, M., Kizaki, T., Oh-ishi, S., Sato, Y. and Ohno, H. (1995). J. Appl. Physiol. 78: 384-387). In order to examine if unloading also increases the BAT activity in rat pups, the hindlimbs in the suspended pups were unloaded by tail suspension beginning on postnatal day 4 and suspended until day 21. The thermogenic activity (which was assessed by guanosine 5'-diphosphate binding to BAT mitochondria) was markedly lower in 21-day-old suspended pups than in 21-day-old control pups, although there was no difference in uncoupling protein 1 (UCP1) content or UCP1 mRNA expression in the BAT mitochondrial fraction between both pups. Likewise, there was no disparity in either adrenal or thymus mass between the control and suspended pups throughout the experiment. These results suggest that, in contrast to adult rats, chronic hindlimb suspension leads to a decrease in the thermogenic activity in BAT of rat pups possibly for reason that pups are less susceptible to the stress of unloading.
Ohira
Y
Y
Department of Physiology and Biomechanics, National Institute of Fitness and Sports, Kanoya, Japan.
Tanaka
T
T
Segawa
M
M
Kizaki
T
T
Ookawara
T
T
Oh-ishi
S
S
Ohno
H
H
D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000375:Aging / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001833:Body Temperature Regulation / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism; D007473:Ion Channels; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D009929:Organ Size; D012333:RNA, Messenger / Q000302:isolation & purification; D051381:Rats; D017208:Rats, Wistar; D014475:Uncoupling Agents / Q000378:metabolism*; D000071256:Uncoupling Protein 1; D018474:Weightlessness Simulation
D002352:Carrier Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; C000604373:Ucp1 protein, rat; D014475:Uncoupling Agents; D000071256:Uncoupling Protein 1; D006153:Guanosine Diphosphate