Michaels J E, Garfield S A, Hung J T, Cardell R R
Department of Anatomy and Cell Biology, University of Cincinnati College of Medicine, Ohio 45267-0521.
Am J Anat. 1990 Aug;188(4):419-28. doi: 10.1002/aja.1001880410.
The effects of short- and long-term stimulation of glycogen synthesis elicited by dexamethasone were studied by light (LM) and electron (EM) microscopic radioautography (RAG) and biochemical analysis. Adrenalectomized rats were fasted overnight and pretreated for short- (3 hr) or long-term (14 hr) periods with dexamethasone prior to intravenous injection of tracer doses of 3H-galactose. Analysis of LM-RAGs from short-term rats revealed that about equal percentages (44%) of hepatocytes became heavily or lightly labeled 1 hr after labeling. The percentage of heavily labeled cells increased slightly 6 hr after labeling, and unlabeled glycogen became apparent in some hepatocytes. The percentage of heavily labeled cells had decreased somewhat 12 hr after labeling, and more unlabeled glycogen was evident. In the long-term rats 1 hr after labeling, a higher percentage of heavily labeled cells (76%) was observed compared to short-term rats, and most glycogen was labeled. In spite of the high amount of labeling seen initially, the percentage of heavily labeled hepatocytes had decreased considerably to 55% by 12 hr after injection; and sparsely labeled and unlabeled glycogen was prevalent. The EM-RAGs of both short- and long-term rats were similar. Silver grains were associated with glycogen patches 1 hr after labeling; 12 hr after labeling, the glycogen patches had enlarged; and label, where present, was dispersed over the enlarged glycogen clumps. Analysis of DPM/mg tissue corroborated the observed decrease in label 12 hr after administration in the long-term animals. The loss of label observed 12 hr after injection in the long-term pretreated rats suggests that turnover of glycogen occurred during this interval despite the net accumulation of glycogen that was visible morphologically and evident from biochemical measurement.
通过光学显微镜（LM）和电子显微镜（EM）放射自显影术（RAG）以及生化分析，研究了地塞米松引起的糖原合成短期和长期刺激的影响。将肾上腺切除的大鼠禁食过夜，并在静脉注射示踪剂量的3H-半乳糖之前，用地塞米松进行短期（3小时）或长期（14小时）预处理。对短期处理大鼠的LM-RAG分析显示，标记后1小时，约相同比例（44%）的肝细胞被重度或轻度标记。标记后6小时，重度标记细胞的比例略有增加，一些肝细胞中出现了未标记的糖原。标记后12小时，重度标记细胞的比例有所下降，更多未标记的糖原明显可见。在长期处理的大鼠中，标记后1小时，与短期处理的大鼠相比，观察到更高比例的重度标记细胞（76%），并且大多数糖原被标记。尽管最初观察到大量标记，但注射后12小时，重度标记肝细胞的比例已大幅降至55%；稀疏标记和未标记的糖原普遍存在。短期和长期处理大鼠的EM-RAG相似。标记后1小时，银颗粒与糖原斑块相关；标记后12小时，糖原斑块增大；并且标记（如果存在）分散在增大的糖原团块上。对每毫克组织中每分钟衰变数（DPM）的分析证实了长期处理动物给药后12小时观察到的标记减少。长期预处理大鼠注射后12小时观察到的标记损失表明，尽管从形态学上可见糖原的净积累并且从生化测量中明显可见，但在此期间糖原发生了周转。
