Fujio T, Fujihara H, Shibata M, Yamada S, Onaka T, Tanaka K, Morita H, Dayanithi G, Kawata M, Murphy D, Ueta Y
Department of Occupational Health, Matsushita Science Center of Industrial Hygiene, Kadoma, Japan.
J Neuroendocrinol. 2006 Oct;18(10):776-85. doi: 10.1111/j.1365-2826.2006.01476.x.
We examined the effects of chronic salt loading on the hypothalamic expressions of the enhanced green fluorescent protein (eGFP), arginine vasopressin (AVP) and oxytocin (OXT) genes in AVP-eGFP transgenic rats that expressed eGFP in the hypothalamic AVP-containing neurones. In these rats, salt loading for 5 days caused a marked increase of the eGFP fluorescence in the magnocellular divisions of the paraventricular nucleus (PVN), the supraoptic nucleus (SON) and the internal layer of the median eminence. Expression of the eGFP gene was increased seven- to eight-fold in the PVN and SON of salt-loaded rats in comparison with euhydrated rats. By contrast, none of these changes were observed in the suprachiasmatic nucleus. The expression of the AVP and OXT genes was increased 1.5- to two-fold in the PVN and SON of salt-loaded nontransgenic (control) and transgenic rats. There were no differences in the expression levels of the AVP and OXT genes in the PVN and SON between nontransgenic (control) and transgenic animals under normal conditions and after salt loading. In the posterior pituitary gland, the intensity of the eGFP fluorescence did not change after salt loading for 5 days, but increased after 10 days of salt loading. Upon salt loading, significant increases in the plasma AVP concentrations, plasma osmolality and plasma Na+ were observed. Furthermore, there were no significant differences in changes of water intake, food intake, urine volume, urine osmolality, urine Na+ concentrations, and the body weights in both models under normal or salt-loaded conditions. Our results show that the response of the AVP-eGFP fusion gene to chronic salt loading is exaggerated, and humoral responses such as AVP and OXT and the body fluid homeostasis are maintained in AVP-eGFP transgenic rats. The AVP-eGFP transgenic rat gives us a new opportunity to study the dynamics of the AVP system in vivo.
我们研究了慢性盐负荷对下丘脑视上核含精氨酸加压素（AVP）神经元中表达增强型绿色荧光蛋白（eGFP）的AVP-eGFP转基因大鼠下丘脑eGFP、AVP和催产素（OXT）基因表达的影响。在这些大鼠中，5天的盐负荷导致室旁核（PVN）、视上核（SON）和正中隆起内层的大细胞部eGFP荧光显著增加。与正常水合大鼠相比，盐负荷大鼠PVN和SON中eGFP基因的表达增加了7至8倍。相比之下，在视交叉上核中未观察到这些变化。盐负荷的非转基因（对照）和转基因大鼠的PVN和SON中，AVP和OXT基因的表达增加了1.5至2倍。在正常条件下和盐负荷后，非转基因（对照）和转基因动物的PVN和SON中AVP和OXT基因的表达水平没有差异。在垂体后叶，5天盐负荷后eGFP荧光强度没有变化，但10天盐负荷后增加。盐负荷后，血浆AVP浓度、血浆渗透压和血浆Na⁺显著增加。此外，在正常或盐负荷条件下，两种模型的水摄入量、食物摄入量、尿量、尿渗透压、尿Na⁺浓度和体重变化均无显著差异。我们的结果表明，AVP-eGFP融合基因对慢性盐负荷的反应被夸大，并且AVP-eGFP转基因大鼠中维持了AVP和OXT等体液反应以及体液稳态。AVP-eGFP转基因大鼠为我们在体内研究AVP系统的动态变化提供了新的机会。
