Wasicko M J, Breitwieser G E, Kim I, Carroll J L
Johns Hopkins University School of Medicine, Johns Hopkins Children's Center, Baltimore, MD, United States.
Respir Physiol Neurobiol. 2006 Dec;154(3):356-71. doi: 10.1016/j.resp.2006.01.003. Epub 2006 Feb 8.
This study examines developmental changes in CB glomus cell depolarization, intracellular calcium (Ca(2+)) and the magnitude of an O(2)-sensitive background ionic conductance that may play roles in the postnatal increase in oxygen sensitivity of glomus cells isolated from rats of 1-3 days and 11-14 days postnatal age. Using fura-2 and perforated patch whole cell recordings, we simultaneously measured Ca(2+) and membrane potential (E(m)) during normoxia and hypoxia. Resting E(m) in normoxia was similar at both ages. Hypoxia caused a larger E(m) depolarization and correspondingly larger Ca(2+) response in glomus cells from 11- to 14-day-old rats compared to 1-3-day-old rats. E(m) and Ca(2+) responses to 40mM K(+) were identical between the two age groups. Under normoxic conditions both age groups had similar background conductances. Under anoxic conditions (at resting membrane potential) background K(+) conductance decreased significantly more in cells from 11- to 14-day-old rats compared to cells from 1- to 3-day-old rats. Glomus cells from newborns therefore have less O(2)-sensitive background K(+) conductance. These results support the hypothesis that postnatal maturation of glomus cell O(2) sensitivity involves developmental regulation of the expression and/or O(2)-sensitivity of background ionic conductances.
本研究考察了颈动脉体球细胞去极化、细胞内钙（Ca(2+)）以及一种对氧敏感的背景离子电导的发育变化，这些变化可能在出生后1 - 3天和11 - 14天龄大鼠分离的球细胞氧敏感性增加中发挥作用。使用fura - 2和穿孔膜片全细胞记录，我们在常氧和低氧条件下同时测量了Ca(2+)和膜电位（E(m)）。两个年龄段在常氧下的静息E(m)相似。与1 - 3天龄大鼠相比，低氧导致11 - 14天龄大鼠的球细胞中E(m)去极化幅度更大，相应地Ca(2+)反应也更大。两个年龄组对40mM K(+)的E(m)和Ca(2+)反应相同。在常氧条件下，两个年龄组的背景电导相似。在缺氧条件下（在静息膜电位时），与1 - 3天龄大鼠的细胞相比，11 - 14天龄大鼠的细胞中背景K(+)电导显著降低更多。因此，新生大鼠的球细胞具有较低的对氧敏感的背景K(+)电导。这些结果支持了这样的假设，即球细胞氧敏感性的出生后成熟涉及背景离子电导的表达和/或氧敏感性的发育调控。
