中文摘要：

配制含0%、15%和30%糊化玉米淀粉的等能饲料分别作为对照、中水平和高水平碳水化合物（CHO）饲料,以体重为50.5±0.6g的南方鲇幼鱼为实验对象,在水温27.5±0.5℃的条件下以对照饲料驯化15d后,分别测定了以三种饲料投喂的南方鲇在餐后3、6、12、24和48h的己糖激酶（HK）、葡萄糖激酶（GK）和磷酸果糖激酶（PFK-1）的活性和血糖水平.结果发现,中、高水平CHO组HK活性在餐后24h时显著高于对照组（P＜0.05）,其余时间点各组间无显著差异;GK活性随CHO水平增加而增加,但其活性的绝对值远低于HK;PFK-1活性在各组间及同组内各时间点均无显著差异.通过分析认为,南方鲇体内葡萄糖磷酸化主要由HK催化,但其活性受饲料CHO水平的影响不明显;GK活性受饲料CHO的诱导而增高,使葡萄糖磷酸化加速,但最大增幅不超过30%;此外,催化果糖-6-磷酸进一步转化为果糖-1,6-二磷酸的PFK-1活性不受饲料CHO水平的影响,因此糖酵解过程的这两个代谢环节均不能在鱼体吸收高糖营养后有效地加速,这应当是该肉食性鱼类在高水平CHO营养条件下产生高血糖积累的重要原因.实验结果表明,血糖变化呈现先升高后降低的趋势,中水平和高水平CHO组的血糖峰值均出现在餐后12h,这作为在该类研究中设定血液取样时间的实验依据.

英文摘要：

Three isoenergetic diets containing 0%, 15 % and 30% gelatinized corn starch were formulated as control, middle level and high level carbohydrate （CHO） diets, respectively. The juvenile southern catfish, Silurus meridionalis Chen（50.5 ± 0.6g） were acclimated with control diet for 15d at 27.5 ± 0.5℃ . Activities of glycolytie key enzymes （HK, GK and PFK-1 ） and the serum glucose concentrations in the southern catfish respectively fed with the three diets were examined, at 3,6,12,24 and 48h after feeding. The results showed that HK activity in the middle and high CHO groups were significantly higher than that in the control group（ P 〈 0.05） at 24h, but no significant difference was found at other time; GK activity was related positively with CHO level, and the absolute measurement of its activity was much lower than that of HK;PFK-1 activity was not significantly different among the three treatments at each measuring time. The results suggested that the glucose phosphorylation in the fish is catalyzed mainly by HK, but its activity could not be significantly induced by dietary CHO level; GK activity was induced by dietary CHO level so that glucose phosphorylation was promoted, but efficiency of the promotion was not more than 30%. In addition, activity of PFK-1 which would catalyze fruetose-6-phosphate into fructose 1,6-bisphosphate did not change at different CHO levels, therefore both metabolic mechanisms in glycolysis could not significantly accelerate with the serum glucose concentrations increasing, which might explain the hyperglycemia in the carnivorous fish with nutrition condition of high dietary CHO level. Serum glucose concentration in either the middle or the high CHO groups primarily increased gradually to its peak at 12h after feeding, and then decreased to the basic level, which could provided experimental basis for designing blood sampling time in this kind of research.