Interaction between heat acclimation and exogenous insulin in brown adipose tissue of rats.
Seventy-one male Wistar strain rats (7 weeks old) were kept at 5, 25, or 34 degrees C, respectively, for 2 weeks with or without insulin administration. Insulin (Novo Lente MC) was given subcutaneously in a dose of 3.62 nmol/125 microliters saline per 100 g body weight. An apparent effect of insulin treatment was noted only in heat-exposed rats, resulting in a remarkable gain in interscapular brown adipose tissue (BAT) mass of heat-acclimated, insulin-treated rats in terms of weight or weight per unit body weight. The BAT from heat-acclimated, insulin-treated rats had significantly higher levels of protein, DNA, RNA, and triglyceride than BAT from heat-acclimated, saline-treated rats. Therefore, it seems likely that the growth of BAT in heat-acclimated, insulin-treated rats was mostly due to the anabolic effects of insulin. The uncoupling protein mRNA was, however, present in BAT of heat-acclimated, insulin-treated rats at rather a depressed level, explaining a corresponding decrease in cold tolerance. On the other hand, the expression of insulin receptor mRNA was attenuated in BAT of rats from all the insulin-treated groups, possibly due to the down-regulation of insulin. Thus, there appeared to be some linkage among BAT, heat acclimation, and insulin.
Ohno
H
H
Department of Hygiene, National Defense Medical College, Tokorozawa, Japan.
Yamashita
H
H
Sato
N
N
Habara
Y
Y
Gasa
S
S
Nagasawa
J
J
Sato
Y
Y
Ishikawa
M
M
Segawa
M
M
Yamamoto
M
M
D000064:Acclimatization / Q000502:physiology*; D002001:Adipose Tissue, Brown / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D006358:Hot Temperature; D007328:Insulin / Q000494:pharmacology; D007473:Ion Channels; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D024101:Mitochondrial Proteins; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000071256:Uncoupling Protein 1
D002352:Carrier Proteins; D007328:Insulin; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D000071256:Uncoupling Protein 1