Scarpace P J, Mooradian A D, Morley J E
Geriatric Research, Education and Clinical Center, Veterans Administration Medical Center, Sepulveda.
J Gerontol. 1988 May;43(3):B65-70. doi: 10.1093/geronj/43.3.b65.
The ability to regulate body temperature diminishes with age. In the rat, nonshivering thermogenesis in brown adipose tissue (BAT) serves as the regulator of body temperature. This process is stimulated by catecholamine activation of adenylate cyclase through the beta-adrenergic receptor. However, beta-adrenergic responsiveness also diminishes with age. To investigate the age-related alterations in beta-adrenergic function in BAT, beta-adrenergic receptor number and cytochrome c oxidase activity were assessed in 3-, 12-, and 24-month-old rats, and adenylate cyclase activity was assessed in 3-, 12-, 18-, and 24-month-old rats. The amount of brown adipose tissue recovered from senescent rats was 30% less than that from either the 3- or 12-month-old rats. There was a corresponding decrease in the total amount of cytochrome c oxidase activity in the 24-month-old rats. In the senescent rats, the density of beta-adrenergic receptors was twofold less than in the 3- and 12-month-old rats. The decrease in density was predominately due to a decrease in the beta 1-adrenergic subtype. Isoproterenol- and NaF-stimulated adenylate cyclase activity were threefold greater and forskolin-stimulated activity was fourfold greater in the 3-month than in the older rats. There was no change in the Kact for isoproterenol with age. These biochemical alterations with age may contribute to the inability of older animals to thermoregulate when exposed to cold.
调节体温的能力会随着年龄增长而下降。在大鼠中，棕色脂肪组织（BAT）中的非颤抖性产热是体温的调节机制。这一过程由儿茶酚胺通过β-肾上腺素能受体激活腺苷酸环化酶来刺激。然而，β-肾上腺素能反应性也会随着年龄增长而下降。为了研究BAT中β-肾上腺素能功能随年龄的变化，对3个月、12个月和24个月大的大鼠进行了β-肾上腺素能受体数量和细胞色素c氧化酶活性的评估，并对3个月、12个月、18个月和24个月大的大鼠进行了腺苷酸环化酶活性的评估。从衰老大鼠中回收的棕色脂肪组织量比3个月或12个月大的大鼠少30%。24个月大的大鼠中细胞色素c氧化酶活性总量相应下降。在衰老大鼠中，β-肾上腺素能受体的密度比3个月和12个月大的大鼠低两倍。密度的下降主要是由于β1-肾上腺素能亚型的减少。与老年大鼠相比，3个月大的大鼠中异丙肾上腺素和氟化钠刺激的腺苷酸环化酶活性高两倍，福斯高林刺激的活性高四倍。异丙肾上腺素的Kact值不会随年龄变化。这些随年龄的生化改变可能导致老年动物在暴露于寒冷时无法进行体温调节。
