Department of Psychology, University of British Columbia, Vancouver, Canada.
PLoS One. 2010 Dec 29;5(12):e15727. doi: 10.1371/journal.pone.0015727.
The brain and other organs locally synthesize steroids. Local synthesis is suggested when steroid levels are higher in tissue than in the circulation. However, measurement of both circulating and tissue steroid levels are subject to methodological considerations. For example, plasma samples are commonly used to estimate circulating steroid levels in whole blood, but steroid levels in plasma and whole blood could differ. In addition, tissue steroid measurements might be affected by blood contamination, which can be addressed experimentally by using saline perfusion to remove blood. In Study 1, we measured corticosterone and testosterone (T) levels in zebra finch (Taeniopygia guttata) plasma, whole blood, and red blood cells (RBC). We also compared corticosterone in plasma, whole blood, and RBC at baseline and after 60 min restraint stress. In Study 2, we quantified corticosterone, dehydroepiandrosterone (DHEA), T, and 17β-estradiol (E₂) levels in the brains of sham-perfused or saline-perfused subjects. In Study 1, corticosterone and T concentrations were highest in plasma, significantly lower in whole blood, and lowest in RBC. In Study 2, saline perfusion unexpectedly increased corticosterone levels in the rostral telencephalon but not other regions. In contrast, saline perfusion decreased DHEA levels in caudal telencephalon and diencephalon. Saline perfusion also increased E₂ levels in caudal telencephalon. In summary, when comparing local and systemic steroid levels, the inclusion of whole blood samples should prove useful. Moreover, blood contamination has little or no effect on measurement of brain steroid levels, suggesting that saline perfusion is not necessary prior to brain collection. Indeed, saline perfusion itself may elevate and lower steroid concentrations in a rapid, region-specific manner.
大脑和其他器官局部合成类固醇。当组织中的类固醇水平高于循环中的水平时，就表明存在局部合成。然而，循环和组织类固醇水平的测量都受到方法学考虑的影响。例如，血浆样本通常用于估计全血中的循环类固醇水平，但血浆和全血中的类固醇水平可能不同。此外，组织类固醇测量可能会受到血液污染的影响，实验中可以通过使用生理盐水灌注来去除血液来解决这个问题。在研究 1 中，我们测量了斑胸草雀（Taeniopygia guttata）血浆、全血和红细胞（RBC）中的皮质酮和睾酮（T）水平。我们还比较了基线和 60 分钟束缚应激后血浆、全血和 RBC 中的皮质酮。在研究 2 中，我们量化了假灌注或生理盐水灌注的动物大脑中的皮质酮、脱氢表雄酮（DHEA）、T 和 17β-雌二醇（E₂）水平。在研究 1 中，皮质酮和 T 浓度在血浆中最高，在全血中显著降低，在 RBC 中最低。在研究 2 中，生理盐水灌注出人意料地增加了额前脑的皮质酮水平，但其他区域没有增加。相比之下，生理盐水灌注降低了后脑和间脑的 DHEA 水平。生理盐水灌注还增加了后脑的 E₂水平。总之，在比较局部和全身类固醇水平时，包含全血样本将是有用的。此外，血液污染对脑类固醇水平的测量几乎没有影响，这表明在收集脑样本之前不需要生理盐水灌注。事实上，生理盐水灌注本身可能会以快速、特定区域的方式升高和降低类固醇浓度。
