Mehrani H, Storey K B
Institute of Biochemistry, Carleton University, Ottawa, ON, Canada.
Biochem Cell Biol. 1993 Nov-Dec;71(11-12):501-6. doi: 10.1139/o93-072.
To analyze the mechanisms of glycogen phosphorylase control in organs of the rainbow trout Oncorhynchus mykiss, activities of glycogen phosphorylase kinase (GPK) and cAMP-dependent protein kinase (PKA), as well as levels of cAMP, were quantified. The complete cascade for activating glycogen phosphorylase was present in trout organs and all components were activated in white skeletal muscle and liver during exhaustive swimming exercise. GPK and PKA showed the highest activities in the liver, being three- and four-fold higher than corresponding activities in white muscle. Exercise stimulated a 60% increase in GPK activity in the liver and a 40% rise in white muscle. Furthermore, the amount of active PKA rose from 12 to 21% in the liver and from 32 to 57% in white muscle after exhaustive exercise and the cellular levels of cAMP increased by 50% in the liver and 70% in white muscle of exercised fish. Other organs (heart, gill, brain, kidney) showed little or no change in these parameters as a result of exhaustive exercise. GPK activity in liver, muscle, and heart extracts was strongly stimulated by in vitro incubation with the catalytic subunit of mammalian PKA, activity rising by 6- to 7-fold in white muscle extracts and 2- to 2.6-fold in liver and heart extracts. This occurred in extracts from both control and exercised fish and suggested that even in fish exercised to exhaustion, the maximal enzymatic potential for activation of glycogenolysis was not expressed.(ABSTRACT TRUNCATED AT 250 WORDS)
为分析虹鳟鱼（Oncorhynchus mykiss）各器官中糖原磷酸化酶的调控机制，对糖原磷酸化酶激酶（GPK）和环磷酸腺苷（cAMP）依赖性蛋白激酶（PKA）的活性以及cAMP水平进行了定量分析。在虹鳟鱼器官中存在激活糖原磷酸化酶的完整级联反应，在剧烈游泳运动期间，白色骨骼肌和肝脏中的所有组分均被激活。GPK和PKA在肝脏中的活性最高，分别比白色肌肉中的相应活性高3倍和4倍。运动刺激肝脏中GPK活性增加60%，白色肌肉中增加40%。此外，剧烈运动后，肝脏中活性PKA的量从12%升至21%，白色肌肉中从32%升至57%，且运动鱼肝脏中的cAMP细胞水平增加50%，白色肌肉中增加70%。其他器官（心脏、鳃、脑、肾）在剧烈运动后这些参数几乎没有变化。用哺乳动物PKA的催化亚基进行体外孵育，强烈刺激肝脏、肌肉和心脏提取物中的GPK活性，白色肌肉提取物中的活性增加6至7倍，肝脏和心脏提取物中的活性增加2至2.6倍。对照鱼和运动鱼的提取物均出现这种情况，这表明即使是运动至疲惫的鱼，糖原分解激活的最大酶促潜力也未得到发挥。（摘要截选至250词）
