Lymangrover J R, Valego N K, Shilling R D
Department of Physiology and Pharmacology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27103.
Mech Ageing Dev. 1988 Jun;43(3):269-78. doi: 10.1016/0047-6374(88)90036-x.
A comparison was made of the resting membrane potential (MP) as well as the MP responses to K+, ACTH and gamma-MSH of superfused adrenocortical, zona fasciculata cells from young (Y) and old (O) male rats. The resting MP of these cells did not vary with age. However, the MP responses to altered extracellular [K+] varied significantly with age. A prolonged biphasic depolarization was observed following ACTH administration; these responses were significantly reduced in O cells. In contrast, stimulation with gamma-MSH did not consistently elicit depolarization in the Y but caused a consistent and prominent depolarization in O cells. These findings suggest that aging is associated with changes in primary membrane events which could explain the reduced ACTH-stimulated steroidogenesis associated with age. Elevated cellular responses to gamma-MSH may contribute to a maintenance of, or increase in, circulating corticosterone levels in aged rats.
对年轻（Y）和老年（O）雄性大鼠的肾上腺皮质束状带细胞进行了比较，研究了其静息膜电位（MP）以及MP对钾离子、促肾上腺皮质激素（ACTH）和γ-促黑素（γ-MSH）的反应。这些细胞的静息MP并不随年龄而变化。然而，MP对细胞外[K⁺]变化的反应随年龄有显著差异。给予ACTH后观察到双相去极化延长；这些反应在老年细胞中显著降低。相反，γ-MSH刺激在年轻细胞中并不能持续引起去极化，但在老年细胞中却能引起持续且明显的去极化。这些发现表明，衰老与初级膜事件的变化有关，这可能解释了与年龄相关的ACTH刺激的类固醇生成减少。细胞对γ-MSH反应的增强可能有助于维持或增加老年大鼠循环皮质酮水平。
