Initial expression of the common alpha-chain in hypophyseal pars tuberalis-specific cells in spontaneous recrudescent hamsters
Initial expression of the common alpha-chain in hypophyseal pars tuberalis-specific cells in spontaneous recrudescent hamsters
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DOI：
10.1210/en.138.10.4101
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发表时间：
1997-10-01
期刊：
影响因子：
4.8
通讯作者：
Kreutz, MR
中科院分区：
文献类型：
--
作者：
Bockers, TM;Bockmann, J;Kreutz, MR
当暴露在短日照条件下时，仓鼠和其他长日照繁殖者会经历性腺退化。然而，随着长期暴露于短日照，动物变得对光不敏感，性腺复发发生。这种不敏感性的潜在机制仍然未知。然而，越来越多的证据表明，垂体结节部（PT）的特定细胞介导这些光周期/非光周期依赖性变化，作为内分泌系统的直接或间接“Zeitgeber”。（β-TSH，β-LH，PRL，共同α链）在长光周期（LP）和18，28，短光周期（SP）38周。如性腺和体重所示，仓鼠在SP治疗18周和28周后显示性腺退化; SP治疗38周后，所有动物均显示复发。在IS和28周的SP，只有PRL的mRNA和蛋白质水平显着降低，在PD和LP值后38周的SP。下丘脑酪氨酸羟化酶的表达在弓状核的免疫细胞化学和原位杂交测定也下调SP18和SP28与SP38的水平增加。SP组尿6-硫酸氧褪黑激素水平升高，以SP18组最高，PT组尿β-TSH mRNA和蛋白均未检测到，而LP组尿β-TSH mRNA和蛋白为中等信号。然而，共同的α-链mRNA和蛋白质，这也减少了动物的SP18组，已经升高后28周的SP和近38周的SP后达到LP水平。这些结果表明，在对比LH和TSH，PRL的表达在PD是一个敏感的指标，光周期依赖性变化的内分泌系统，似乎是酪氨酸羟化酶独立。PT特异性细胞中常见α链表达的增加取决于PD中激素变化之前SP的持续时间，这使我们推测PT特异性细胞通过PT-PD途径启动自发复发。
When-exposed to short-day conditions, hamsters and other long-day breeders undergo gonadal regression. With chronic exposure to short days, however, the animals become photorefractory and gonadal recrudescence occurs. The underlying mechanism for this insensitivity is still unknown. There is growing evidence, however, that specific cells of the pituitary pars tuberalis (PT) mediate these photoperiod/nonphotoperiod-dependent changes as a direct or indirect ''Zeitgeber'' for the endocrine system.We investigated messenger RNA (mRNA)/protein formation for several hypophyseal hormones (beta-TSH, beta-LH, PRL, common alpha-chain) in the pars distalis (PD) and PT of female Djungarian hamsters in long photoperiod (LP) and after 18, 28, and 38 weeks of short photoperiod (SP). As indicated by gonadal and body weight, the hamsters displayed gonadal regression after 18 and 28 weeks of SP; after 38 weeks of SP, all animals showed recrudescence. At Is and 28 weeks of SP, only PRL mRNA and protein levels were significantly reduced in the PD and returned to LP values after 38 weeks of SP. The expression of hypothalamic tyrosine hydroxylase in the arcuate nucleus that was determined by immunocytochemistry and by in situ hybridization was also down-regulated in SP18 and SP28 with increasing levels at SP38. Urinary 6-sulfatoxymelatonin levels were elevated in SP with highest levels in the SP18 group.In the PT, beta-TSH mRNA and protein were not detectable in all SP groups compared with the moderate signal intensity in LP. The common alpha-chain mRNA and protein, however, which were also reduced in the animals of the SP18 group, were already elevated after 28 weeks of SP and nearly reached LP-levels after 38 weeks of SP.These results show that, in contrast to LH and TSH, PRL expression in the PD is a sensitive indicator for photoperiod dependent changes of the endocrine system and seems to be tyrosine hydroxylase independent. The increase of common alpha-chain expression in PT-specific cells depending upon duration of SP that precedes the hormonal changes in the PD leads us to speculate that PT-specific cells initiate spontaneous recrudescence via a PT-PD pathway.