Armbrecht H J, Birnbaum L S, Zenser T V, Davis B B
Exp Gerontol. 1982;17(1):41-8. doi: 10.1016/0531-5565(82)90007-9.
There are changes in the mixed function oxidase enzymatic activities of rat hepatic microsomal membranes with age. However, the protein components of the mixed function oxidase system do not appear to change with age. The purpose of this study was to detect possible changes in the fluidity of the lipid component of the microsomal membrane with age. Hepatic microsomes were isolated by differential centrifugation from uninduced, male CFN rats aged 3, 12 and 26 mo. The microsomal membrane fluidity was measured using electron paramagnetic resonance after incorporation of a 5-nitroxide stearic acid spin label into the membrane. The order parameter S decreased with age from 0.586 +/- 0.003 (3 mo) to 0.581 +/- 0.002 (12 mo) to 0.569 +/- 0.003 (26 mo) at 30 degrees C. This indicated an increase in membrane fluidity with age. In membranes labeled with the 16-nitroxide stearic acid, a similar increase in membrane fluidity with age was observed. The order parameter of microsomal membranes from 3 and 26 mo rats was measured over the temperature range 10 degrees to 31 degrees C in steps of 0.9 degrees C. A plot of the log of S versus the reciprocal temperature revealed a phase transition at 24 degrees C in membranes from 26 mo rats, but no phase transition was observed in 3 mo old rats in this temperature range. The change in fluidity of the hepatic microsomal membrane with age may account for some of the observed changes in membrane-bound mixed function oxidase activities with age.
大鼠肝微粒体膜的混合功能氧化酶活性随年龄增长而发生变化。然而，混合功能氧化酶系统的蛋白质成分似乎并不会随年龄而改变。本研究的目的是检测微粒体膜脂质成分的流动性是否会随年龄增长而发生可能的变化。通过差速离心法从3个月、12个月和26个月大的未诱导雄性CFN大鼠中分离出肝微粒体。在将5-硝基硬脂酸自旋标记掺入膜中后，使用电子顺磁共振测量微粒体膜的流动性。在30℃时，有序参数S随年龄增长而降低，从0.586±0.003（3个月）降至0.581±0.002（12个月），再降至0.569±0.003（26个月）。这表明膜流动性随年龄增长而增加。在用16-硝基硬脂酸标记的膜中，也观察到膜流动性随年龄有类似的增加。以0.9℃的步长测量了3个月和26个月大鼠微粒体膜在10℃至31℃温度范围内的有序参数。S的对数与温度倒数的关系图显示，26个月大鼠的膜在24℃出现相变，但在该温度范围内3个月大的大鼠未观察到相变。肝微粒体膜流动性随年龄的变化可能解释了所观察到的膜结合混合功能氧化酶活性随年龄的一些变化。
