异育银卿口服葡萄糖后血糖、血脂和肝糖原的变化

禁食 4周后对体重为 46± 5g的异育银鲫进行了葡萄糖耐量试验。口服 16 7mg·(10 0g) -1体重的葡萄糖之前及之后的 1、2、3、4、5、6、8、10、14、18和 2 4h分别抽血、取肝胰腺 ,分析血糖、血脂和肝糖原含量。实验结果表明 ,血糖在口服葡萄糖后 3h内迅速升高 ,并于 3h时达最高水平 ,以后逐渐下降。口服葡萄糖后 1h血脂含量最高 ,然后开始下降 ,并于 8h时又开始升高。口服葡萄糖后的最初 2h内肝糖原含量显著降低 ,随后开始提高 ,并在 6h时达最高峰。用体重为 (16 4± 12 )g的异育银鲫为材料禁食 4周后灌喂不同剂量的葡萄糖 ,研究葡萄糖剂量对血糖和肝糖原变化规律的影响。结果表明 ,随着口服葡萄糖剂量的增加 ,血糖升高幅度加大 ,而肝糖原含量则随葡萄糖剂量增加而减少。上述实验结果提示异育银鲫在胰岛素的分泌方面与哺乳类存在本质的不同。     

Investigation of the nutritional requirements of Australian snapper Pagrus auratus (Bloch & Schneider 1801): digestibility of gelatinized wheat starch and clearance of an intra-peritoneal injection of d-glucose

Two experiments were performed to investigate the digestibility and utilization of carbohydrate sources by Australian snapper Pagrus auratus. In the first experiment, snapper of two different size classes (110 and 375 g) were fed a reference diet containing no starch (REF) or diets containing 150 (PN15), 250 (PN25), 350 (PN35) or 450 g kg^?1 (PN45) of 100% gelatinized wheat starch to investigate the interactive effects of fish size and starch inclusion level on apparent organic matter (OM) or gross energy (GE) digestibility (ADC), post‐prandial plasma glucose concentration, hepatosomatic index (HSI) and liver or tissue glycogen content. A second experiment used a 72 h time course study to investigate the ability of larger snapper (300–481 g) to clear an intra‐peritoneal injection of 1 g d ‐glucose kg^?1 body weight (BW). Organic matter and GE ADCs declined significantly in both fish sizes as the level of starch increased (PN45energy small fishenergy large fish). There was no interaction between fish size and inclusion level with respect to GE or OM ADCs. Gross energy ADC for both sized fish was described by the linear function GE ADC=104.97 (±3.39)–0.109 (±0.010) × inclusion level (R²=0.86). Hepatosomatic index, liver and muscle glycogen concentrations were significantly elevated in both small and large snapper‐fed diets containing gelatinized starch compared with snapper fed the REF diet. Three‐hour post‐prandial plasma glucose concentrations were not significantly affected by fish size, inclusion level or the interaction of these factors (REF=PN15=PN25=PN35=PN45), and ranged between 1.60 and 2.5 mM. The mean±SD resting level of plasma glucose (0 h) was 2.4±1.1 mM. Circulating levels of plasma glucose in snapper peaked at 18.9 mM approximately 3 h after intra‐peritoneal injection and fish exhibited hyperglycaemia for at least 12–18 h. There were no significant differences between the plasma glucose concentrations of snapper sampled 0, 18, 24, 48 or 72 h after injection (0=18=24=48=72<12< 1<3=6 h), indicating snapper required almost 18 h to regulate their circulating levels of glucose to near‐basal concentrations. Australian snapper are capable of digesting moderate levels of gelatinized wheat starch; however, increasing the dietary content of starch resulted in a reduction in OM and GE digestibility. Smaller snapper appear to be less capable of digesting gelatinized starch than larger fish, and levels above 250 and 350 g kg^?1 of diet are not recommended for small and large fish respectively. Snapper subjected to an intra‐peritoneal injection of d ‐glucose have prolonged hyperglycaemia; however, the post‐prandial response to the uptake of glucose from normally digested gelatinized starch appears to be more regulated.     

Changes in plasma glucagon and insulin associated with fasting in sea bass (Dicentrarchus labrax)

Juvenile sea bass (Dicentrarchus labrax) were fasted for 22 days and changes in plasma insulin, glucagon and glucose levels, as well as glycogen and protein content in liver and muscle were analyzed. Glucagon increased initially on the 4th day of fasting. The glucagon/insulin ratio (G/I) increased from a value of 0.11±0.02 (24h of fasting) to 0.21±0.05 (4th day of fasting). Thereafter, both glucagon and insulin levels decreased and remained at low concentrations until the 22nd day of fasting. Plasma glucose levels fell at the beginning of fasting, stabilized between the 4th and 8th day, and gradually declined during the rest of the experiment. There was a body weight loss of 15% and a significant decrease in both the hepatosomatic index and mesenteric fat. The decrease in the percentage of muscle proteins was not significant, while liver glycogen content showed a sharp decline.     

Carbohydrate utilization by juvenile silver perch, Bidyanus bidyanus (Mitchell). I. Uptake and clearance of monosaccharides following intraperitoneal injection

Abstract Intraperitoneal carbohydrate tolerance tests were done to assess the ability of silver perch, Bidyanus bidyanus, to utilize the predominant monosaccharides in plant ingredients currently being used in the formulation of aquaculture feeds for this species. Preliminary experiments carried out to assess baseline plasma glucose concentrations indicated that blood glucose levels were elevated within 2 min of handling and silver perch required a period of 48 h without feeding before plasma glucose levels remained constant. In the first carbohydrate test, either glucose, galactose or xylose were administered by injection into the intraperitoneal cavity at a dose rate of 1 g carbohydrate kg^?1 body weight (BW). In the second carbohydrate test, glucose was administered at a dose rate of either 2 or 4 g glucose kg BW^?1. Following injection, uptake and clearance rate of the carbohydrates from the blood stream was monitored over a 24‐h period. Silver perch were significantly more efficient at the uptake and clearance of glucose from the blood stream than xylose or galactose. Maximum plasma glucose concentrations (22.2 mmol L ^?1) were recorded at 1 h following injection and basal levels (3.44 mm ) were attained between 6 and 12 h following injection. For both galactose and xylose, maximum concentrations were recorded at 1 and 3 h, respectively, and concentrations of both monosaccharides remained significantly elevated 24 h after the administration. Plasma glucose concentrations of silver perch administered with either 2 or 4 g glucose kg BW^?1 were significantly elevated and peaked at similar levels (30.2 mmol L ^?1 and 30.7 mmol L ^?1 respectively) 3 h after injection. Basal plasma glucose concentrations were attained in silver perch injected with 2 g glucose kg BW^?1 at 24 h following administration. Plasma glucose concentrations remained significantly elevated in fish injected with 4 g glucose kg BW^?1 after 24 h. These findings indicate that silver perch are more efficient at utilizing glucose than either xylose or galactose, and that there are also differing maximum threshold for the inclusion of ingredients rich in glucose, galactose and xylose into the diets of silver perch.     

注射葡萄糖对吉富罗非鱼血浆生化指标、胰岛素和糖酵解关键酶的影响

研究注射葡萄糖对吉富罗非鱼(Oreochromis miloticus)生化指标、胰岛素和糖酵解酶的影响。选取体质量约80 g的吉富罗非鱼150尾,随机分为2个实验组,对照组腹腔注射0.7%的无菌生理盐水,处理组按照30 mg/100 g(体质量)的剂量腹腔注射葡萄糖。结果表明:(1)吉富罗非鱼在注射葡萄糖后1 h血糖达到最高水平,而后显著下降(P<0.05),3 h后降低到正常水平。注射葡萄糖可显著提高胆固醇的含量(P<0.05),并显著降低谷草转氨酶水平(P<0.05),但对血浆蛋白、甘油三酯和谷丙转氨酶水平没有显著影响(P>0.05)。(2)肝糖原在葡萄糖注射后的6 h达到最高水平,而后显著下降(P<0.05),肌糖原没有发生变化。(3)血浆和肌肉中的胰岛素均在葡萄糖注射后的3 h达到最高水平,而后显著下降(P<0.05),而肝中的胰岛素水平没有发生变化。(4)丙酮酸激酶的活力在葡萄糖注射后6h达到最高水平(P<0.05),己糖激酶的活力在注射葡萄糖后没有发生变化。结果表明,注射葡萄糖可显著提高吉富罗非鱼血糖水平,且维持时间较长,胰岛素含量和丙酮酸激酶(PK)活力的提高均相对延迟,而己糖激酶活力的不足又限制了葡萄糖的酵解反应,从而引起血浆胆固醇升高,并伴有持续的血糖和肝糖原升高,从而产生营养胁迫的生理反应,加重鱼类对葡萄糖的代谢负担。     

Renal threshold for urinary glucose excretion by tilapia in response to orally administered carbohydrates and injected glucose

Two experiments, oral carbohydrate administration (Experiment 1) and vein glucose injection (Experiment 2), were conducted to gain more insight into the ability of hybrid tilapia, Oreochromis niloticus × O. aureus, to utilize different carbohydrates and to establish the kidney threshold for urinary glucose excretion. In Experiment 1, both glucose and starch were administered orally after the tilapia were fasted for 24 h. Plasma and urine were sampled from the fish at selected time intervals from 1 to 24 h thereafter. Higher (p<0.05) plasma and urine glucose concentrations were found in fish fed on glucose than in fish fed on starch. The concentration of plasma glucose of tilapia peaked at 3 h (25.45 mM for glucose; 8.24 mM for starch) after the oral ingestion of both carbohydrates. Maximum urinary glucose concentrations (48 mM for glucose; 10 mM for starch) in fish fed glucose and starch were at 3 and 4 h post administration. In Experiment 2, five concentrations (0, 0.08, 0.12, 0.16 and 0.24 g glucose ml^–1) of glucose solution were injected into the caudal vein of the tilapia. Urine were sampled from the fish at 30-min time intervals from 0 to 6 h after the injection. Blood was sampled at 1 h after the injection. Higher urinary glucose concentrations were observed in fish injected with 0.12 g glucose ml^–1. When the urinary glucose concentrations in fish injected with the various glucose concentrations were plotted against the plasma glucose concentrations of the fish 1 h after injection, the kidney threshold for urinary glucose excretion in tilapia appeared to be about 6 mM.     

Glycemic and insulin responses in white sea bream Diplodus sargus, after intraperitoneal administration of glucose

A glucose tolerance test was performed in white sea bream Diplodus sargus, juveniles to evaluate the effect of a glucose load on plasma glucose, insulin, triacylglyceride levels, and on liver glycogen storage in order to study the capability of glucose utilization by this species. After being fasted for 48?h, fish were intraperitoneally injected with either 1?g of glucose per kg body weight or a saline solution. Plasma glucose rose from a basal level of 4 to a peak of 18-19?mmol?l(-1), 2-4?h after glucose injection and fish exhibited hyperglycemia for 9?h. An insulin peak (from 0.5 to 0.8?ng?ml(-1)) was observed 2-6?h after glucose injection, and basal value was attained within 9?h. Liver glycogen peaked 6-12?h after the glucose load and thereafter decreased to the basal value which was attained 24?h after injection. Plasma triacylglycerides in glucose-injected fish were only significantly higher than the basal value 12?h after injection. Glucose-injected fish generally showed lower plasma triacylglyceride levels than control fish. Our results indicate that under these experimental conditions, glucose acts as an insulin secretagogue in white sea bream juveniles. Moreover, insulin may have contributed to restoring basal plasma glucose levels by enhancing glucose uptake in the liver. Further studies are needed to corroborate the lipolytic action of glucose. Clearance of glucose from the blood stream was fast, comparatively to other species, indicating that white sea bream has a good capability of glucose utilization.     

腹腔注射葡萄糖对大黄鱼血液生化指标及糖代谢关键酶表达量的影响

为研究大黄鱼对葡萄糖的耐受能力和相关糖代谢关键酶的表达量,选取体质量约为100 g的大黄鱼禁食24 h,随机分为3个实验组,分别为对照组(0.9%的无菌生理盐水,CG组),低剂量葡萄糖组(300 mg/kg体质量,LG组)和高剂量葡萄糖组(1500 mg/kg体质量,HG组)。结果显示,大黄鱼在注射高剂量和低剂量葡萄糖后,血糖均在3 h达到最高水平,且HG组的峰值显著高于LG组,LG组在24 h恢复至正常水平,HG组在24 h仍然高于正常水平。HG组、LG组注射葡萄糖后,HK、GK基因相对表达量均显著上升,其峰值出现在注射后9 h。HG组PFK基因相对表达量在注射后6 h达到峰值。HG组PEPCK基因相对表达量在注射葡萄糖后显著下降,其中最低时间点为2 h。HG组G6PD基因相对表达量在注射后6 h显著高于其他各个时间点。研究表明,注射高、低浓度葡萄糖后,均会提高大黄鱼血糖水平,且能维持较长时间。注射葡萄糖后糖酵解途径关键酶如HK、GK、PFK及糖异生途径关键酶PEPCK基因相对表达量受血糖调节,但G6Pase、FBPase表达量并不因血糖升高而下降。导致注射葡萄糖后,大黄鱼不断产生内源性葡萄糖,这是大黄鱼表现为对高血糖不耐受的原因之一。     

Dietary carbohydrate utilization in cod (Gadus morhua): metabolic responses to feeding and fasting

Moist diets with increasing amounts of carbohydrate (0.5%, 10% and 21% on a dry weight basis) were each fed to duplicate groups of cod (initial weight 370 g) for 8 weeks, after which all groups were fasted for 4 weeks. Protein energy was high and accounted for more than 70% of the gross energy content in all feeds, and the diets were maintained isocaloric by substituting lipid energy for carbohydrate energy. No indigestible binder was added. Excellent growth and feed conversion were obtained in all groups. After 4 weeks of fasting, fish previously fed diets with either 10% or 21% carbohydrate showed significantly higher weight loss than fish fed the diet without carbohydrate. Liver glycogen reached 10% of liver wet weight in fish fed diets containing 10% or 21% carbohydrate and 5% in fish receiving 0.5% carbohydrate after 8 weeks. Following 4 weeks of fasting, liver glycogen was reduced to similar levels in all fish. Plasma glucose levels 4 h after feeding were higher in fish fed the diets with 10% or 21% carbohydrate and plasma free amino acid levels (FAA) were lower, than in fish fed the diet containing 0.5% carbohydrate. Blood lactate concentrations were unaffected during the first 24 h after feeding. After 4 weeks of food deprivation, the levels were significantly reduced only in the 21% carbohydrate group. A link between glucagon and protein metabolism is suggested because plasma glucagon concentration followed the same pattern as the concentrations of plasma FAA throughout the study. Insulin and glucagon-like peptide (GLP) showed a covariation throughout the experiment. Reduced plasma insulin levels were seen after fasting concomitant with reduction in the levels of FAA and glucose. It is suggested that insulin secretion in cod is affected both by plasma FAA and glucose and that cod meets food deprivation by slowing down metabolism.     

饥饿及再投喂处理对草鱼生长、葡萄糖代谢和转运蛋白1表达的影响

设置持续投喂组(C,持续投喂8周)、饥饿再投喂组(R,饥饿4周+再投喂4周)和持续饥饿组(S,饥饿8周)3个处理组,研究3种不同饥饿处理对草鱼(Ctenopharyngodon idellus)血清生化指标、糖原和糖代谢相关酶和葡萄糖转运蛋白1(GLUT1)的影响,同时在此实验基础上研究草鱼在急性高糖负荷胁迫下的糖耐受能力、糖代谢相关酶和GLUT1的变化规律,旨在阐明草鱼在饥饿及再投喂处理条件下的糖代谢特征。选取初重为(125.35±0.54)g的草鱼,饲养8周后以30 mg/100 g体重的剂量腹腔注射葡萄糖研究其糖耐受能力。结果显示,S组肝糖原和血清的血糖、甘油三酯含量均最低。饥饿处理对草鱼糖耐受能力影响显著,S组血糖含量在各时间点上显著低于其余两组(P0.05),肝糖原在6 h达到峰值;饥饿处理对草鱼肝脏糖代谢关键酶影响显著,饥饿处理(S组)诱使磷酸烯醇式丙酮酸激酶(PEPCK)活性上升但抑制丙酮酸激酶(PK)和果糖-6-磷酸激酶(PFK)的活性(P0.05),而饥饿再投喂(R组)后PEPCK、PK和PFK酶活性恢复到持续投喂(C组)处理水平。注射葡萄糖后S组肝脏GK酶活性增幅最大,PK酶活性呈上升趋势,而R组则呈先下降后上升的趋势;饥饿处理对草鱼肝脏和肌肉GLUT1表达影响显著,注射葡萄糖后,除R组肝脏组织外,其余各组草鱼肝脏和肌肉组织GLUT1表达量均呈先上升后下降的趋势,且S组肌肉GLUT1表达量在各个时间点上均高于其余两组(P0.05)。研究结果表明,在不同饥饿处理下,草鱼可通过消耗肝糖原和甘油三酯及降低肝脏糖酵解相关酶(PK和PFK)活性和促进糖异生PEPCK酶活性来应对饥饿胁迫,而饥饿处理可诱使GK和PK酶活性上升、促进糖原合成和激活GLUT1基因的表达和转运来缓解草鱼急性高糖负荷,从而提高其糖耐受能力。     

Effect of gelatinized wheat and maize in diets for large Atlantic salmon (Salmo salar L.) on glycogen retention, plasma glucose and fish health

This publication reports on analytical data from a large-scale experiment, using 3360 Atlantic salmon, Salmo salar L., distributed into 12 sea cages. Salmon were grown from an average 600 g to an average 3.5 kg. Samples for analyses were taken when fish were in the range of 1.8 and 3.5 kg. Dietary changes between groups were increased starch from 24 to 230 g kg^?1 and balanced with protein. The diets were isolipic. All salmon showed small stores of glycogen in all analysed organs, and only in heart, gills and kidney of large fish (3.5 kg) were the levels correlated with dietary starch. Minor differences between groups were found in liver NADPH production, but with substantially decreased NADPH production per g protein as the fish grew from 1.8 to 3.5 kg, indicating that increasing dietary starch did not lead to induction of liver hexokinase, and that the activity of this enzyme may decline as fish size increases. An increase in plasma glucose concentrations was found as dietary starch increased, but all levels were moderate and ranged within reference values. Plasma total protein concentrations did not, however, vary according to decreased dietary protein, but increased substantially in all groups as the fish grew from 1.8 to 3.5 kg. Dietary treatments had no influence on haematological parameters, except for decreased haemoglobin concentrations as dietary starch increased in large fish (3.5 kg). No impared liver function was detected, evaluated by activities of ASAT, ALAT and LDH, and by histological analyses. Low serum lysozyme activities were recorded in all groups, and were not correlated with plasma glucose or liver glycogen concentrations.     

Stages of embryonic development and changes in enzyme activities in embryogenesis of turbot (Scophthalmus maximus L.)

The early development of turbot (Scophthalmus maximus) from fertilization to hatching was described. Hatching occurred at 108 h post-fertilization (hpf) in 14 °C. Yolk syncytial layer and blastocoel formed at morula stage and low stage, respectively. Neural rod derived from the ectoderm appeared and the first somite formed in the middle of the embryonic body at 90 % epiboly stage, and notochord primordium formed at complete epiboly stage. Kupffer’s vesicle appeared at 59 h 35 min hpf and degenerated at 89 hpf. At 72 hpf, the digestive tract formed in the ventral side of the embryonic body, and the posterior digestive tract of embryo was ciliated at 89 hpf. Enzymes play a key role in the catabolism of yolk during embryogenesis of fishes. In this study, the main enzymes alkaline phosphatase (AP), leucine aminopeptidase N (LAP), pepsin, trypsin and Leucine-alanine peptidase (Leu-ala) were all observed in unfertilized eggs and embryo of S. maximus, but amylase was not detected, speculating that amino acids appear to be the main energy substrate during embryonic development of S. maximus, while carbohydrates is less essential. AP reached the lowest value at the gastrula stage and then increased rapidly reaching the highest value at hatching. LAP showed the highest value in unfertilized eggs and kept on decreasing until the blastula stage with the lowest value and then increased at the gastrula stage, followed by a gradual decline thereafter. Trypsin reached the lowest value at the blastula stage and then fluctuated with the maximal value at hatching. Pepsin reached the highest and the lowest values at the unfertilized eggs and the cleavage stage, respectively, but disappeared at hatching. Leu-ala had the maximum activity at the blastula stage and then declined to the minimum at the gastrula stage followed by a gradual increase thereafter.     

The physiological response of the turbot to multiple net confinements

The effects of multiple net confinements on the physiological stress response of the turbot (Scophthalmus maximus L.) were investigated. To allow for repeated blood sampling from individuals, fish were cannulated in the afferent branchial artery and were exposed to multiple 9 min net confinement episodes separated by either 4 h or 24 h. In fish stressed twice 4 h apart cumulative effects in plasma cortisol, glucose and free fatty acid concentrations were evident after the second handling stress. Although plasma Na⁺ and Cl⁻ concentrations were not increased further by the second net confinement, the elevation in plasma concentrations were more sustained compared to turbot handled only once. In a second experiment where turbot were net confined five times, with a 24 h recovery period between each net confinement episode, there was no evidence of any physiological accommodation with repeated exposures. For most circulatory parameters, there was also no evidence of any cumulative effect apparent. Plasma glucose concentrations were, however, elevated to a significantly higher degree with repeated net confinements. Although turbot were tolerant to the handling procedures, with no mortalities recorded, episodes of multiple handling of this species should be separated by at least 24 h if cumulative physiological disturbances are to be avoided. The significance of cumulative increases in plasma glucose concentrations is discussed. Present address: Aquaculture Associates International, The Firs, Glasshouse Hill, Codnor, Derbyshire, DE5 9QT, UK     

Dose-dependent effects of acute melatonin treatments on brain carbohydrate metabolism of rainbow trout

The levels of glycogen, lactate, acetoacetate and -hydroxybutyrate in brain as well as glycogen and lactate levels in liver, and glucose levels in plasma were evaluated in rainbow trout, Oncorhynchus mykiss, injected with ethanol/saline (5/95; v/v) alone (controls) or containing melatonin at three different doses 0.25, 0.5 and 1 mg kg^-1. The results obtained demonstrate, for the first time in a teleost fish, the existence of changes in brain carbohydrate and ketone body metabolism due to melatonin treatment. Thus, a clear dose-dependent decrease was observed in brain and liver glycogen levels, whereas a clear dose-response increase was observed in brain for lactate, acetoacetate and -hydroxybutyrate levels, and in plasma for glucose levels. CO₂ production from glucose was also tested in brains of pooled fish and these rates were not altered by melatonin treatment. Altogether, these results suggest that melatonin may play an indirect role, possibly through alterations in insulin physiology, in the regulation of carbohydrate and ketone body metabolism in brain of rainbow trout.     

Organ responses to 14C-glucose injection in Atlantic halibut, Hippoglossus hippoglossus (L.), acclimated to diet of varying carbohydrate content

After adapting Atlantic halibut, Hippoglossus hippoglossus (L.), to three different levels of available dietary carbohydrate (22, 47 and 82 g kg^-1), the uptake of intraperitoneally injected glucose, both labelled and unlabelled, by the liver, white muscle, plasma, gills, heart, kidney and gastrointestinal wall, as well as concentrations of glucose in plasma and glycogen in organs, were studied. Even 16 h after glucose injection, halibut showed hyperglycaemia. The response, however, was moderate when adapted to the two higher than to the lowest starch diet, indicating some adaptative capacity. A negative correlation was found between plasma glucose and liver glycogen concentrations, hepatosomatic index and liver weight. The amount of glucose restored, relative to the amount injected, demonstrated that adaptation to dietary starch had significant effects on liver glycogen levels, with the highest incorporation of labelled glucose being observed in halibut adapted to the lowest dietary starch level. The amount of labelled glucose restored was highest in liver, followed by muscle > gastrointestinal wall > plasma > gills > kidney and heart, when evaluating the amount in the total organ. An indication of which organ was the most metabolically active in glucose utilization was found by expressing the results on a concentration basis, and it decreased in order, heart > gills > intestinal wall > kidney and muscle.     

Biochemical responses of matrinxãBrycon cephalus (Günther, 1869) after sustained swimming

Juvenile matrinxã, Brycon cephalus, were submitted to sustained swimming for 72 days at 1.0 body length s^?1. Exercised fish (EF) grew more than non‐EF and their feed conversion ratio (FCR) improved; haematological responses demonstrated a decrease in haemoglobin and mean cell haemoglobin contents and increase in the mean cell volume. In the plasma, sodium, ammonia and amino acid concentrations increased; plasma triglycerides decreased while free fatty acids increased. Liver glucose, free amino acids, ammonia, the rate protein per fish weight and total lipid content increased, while the glycogen per fish ratio declined. Glutamate dehydrogenase (GDH) activity increased while pyruvate kinase (PK) and lactate dehydrogenase (LDH) decreased. White muscle glucose, lactate, the glycogen per fish‐weight ratio and total lipid content exhibited a decrease in their values; ammonia, free amino acids and the protein per fish‐weight ratio increased. GDH and PK decreased their activities. In the red muscle glycogen store, the glycogen per fish‐weight ratio and glucose were reduced. Juvenile matrinxãs, under sustained swimming, were physiologically and biochemically adapted to exercise as indicated by improved blood flow, transport and oxygen uptake, FCR, amino acid and protein incorporation and growth. Continuous exercise is a good practice for B. cephalus cultivation.     

饲料中三种不同碳水化合物对大黄鱼生长性能和肝脏糖代谢关键酶活性的影响

为研究饲料中添加3种不同的碳水化合物对大黄鱼生长性能、饲料利用以及糖代谢关键酶活性的影响,进行为期8周的生长实验和持续24 h的饥饿实验。以葡萄糖、小麦淀粉和糊精这3种碳水化合物作为糖源,设计3组等氮等脂(48%粗蛋白和12%粗脂肪)的饲料。选用初始体质量为(8.51±0.02)g的大黄鱼450尾,随机分为3组(每组3个重复,每个重复50尾)。养殖实验结束后进行饥饿实验,分别在饥饿实验开始后的0、1、3、5、7、9、11和24 h取样。结果显示,小麦淀粉组和糊精组大黄鱼的增重率和特定生长率显著高于葡萄糖组,且这2个饲料组的饲料系数显著低于葡萄糖组。糊精组大黄鱼的肝体比显著高于其余2组大黄鱼的肝体比。饲料中添加3种不同碳水化合物对大黄鱼成活率、脏体比和肥满度无显著性影响。葡萄糖组和小麦淀粉组大黄鱼血糖含量在饥饿1 h后都开始显著上升,葡萄糖组高血糖水平持续至少10 h;小麦淀粉组3 h显著下降至初始水平左右,未达到高血糖水平;糊精组大黄鱼血糖含量随着时间的推移持续升高,在11 h达到最大值,高血糖水平持续4 h。饲料中添加3种不同碳水化合物对大黄鱼血清胰岛素和肝糖原含量有显著性影响。小麦淀粉对大黄鱼肝脏葡萄糖激酶(GK)活性的升高有诱导作用。大黄鱼摄食3种不同碳水化合物饲料后鱼体血糖水平升高,但糖异生关键酶如葡萄糖-6-磷酸酶(G6Pase)、果糖-1,6-二磷酸酶(FBPase)和磷酸烯醇式丙酮酸羧激酶(PEPCK)的活性并不降低。饲料中添加葡萄糖和小麦淀粉对大黄鱼肝脏丙酮酸激酶(PK)活性有显著性影响。研究表明,大黄鱼利用结构复杂的多糖(如小麦淀粉和糊精)的能力要高于单糖(如葡萄糖),3种不同碳水化合物对大黄鱼血糖调节及糖酵解和糖异生途径关键酶活性的影响存在差异。     

Physiological responses associated with capture and crowding stress in matrinxãBrycon cephalus (Gunther, 1869)

The dynamics of plasma cortisol, blood glucose, plasma chloride and liver glycogen were investigated in matrinxã (Brycon cephalus) submitted to capture and various periods of crowding. A total of 400 fish (700±22 g weight) were distributed in four ponds divided into four 50‐m² squares (25 fish/square, 350 g L^?1), where they were acclimated for 30 days. On the sampling day, after 24 h without food, all fish from three squares were transferred to the fourth square. Six fish were sampled before the procedure (control group, zero time) and 1, 3, 6 and 24 h after the capture and crowding. Each sampling was performed in a different pond to prevent additional stress. Fish were anaesthetized and blood and liver collected for biochemical analysis. Water temperature, pH, dissolved oxygen, alkalinity, ammonia and nitrite levels were within acceptable levels for matrinxã rearing. Slight but not significant increases were verified in plasma cortisol and blood glucose levels, as were decreases in plasma chloride and liver glycogen levels. The results suggest that matrinxã is highly tolerant to the procedures of capture and short‐term crowding.     

Differences between Atlantic halibut (Hippoglossus hippoglossus L.) and turbot (Scophthalmus maximus L.) in tolerance to acute low temperature exposure

Juvenile Atlantic halibut (Hippoglossus hippoglossus L.) and turbot (Scophthalmus maximus L.) acclimated to 8–9 °C sea water were transferred to sea water at 1 °C for 7 days. An immediate spasm-like response was noticed in the turbot after the transfer, but not in the halibut. None of the fish died. The turbot suffered from substantial physiological disturbances after the transfer. Their blood plasma Cl^– concentration increased and muscle water content decreased markedly. The plasma glucose concentration was several times higher than the control level from day one onwards. A decrease in the haematocrit was recorded some hours after transfer, followed by a marked increase on day 7. In halibut, the plasma Cl^– concentration fell somewhat during the first days, but returned thereafter to its pretransfer level. The muscle water content was unchanged. Both haematocrit and plasma glucose concentration were unchanged until day 7, when both were significantly higher. The differences in the response to low-temperature challenge between halibut and turbot are probably related to genetic differences in temperature tolerance, which reflect differences in the distribution of the species.