Albert D.F. Addink

The effects of cortisol administration on intermediary metabolism in teleost fish

Abstract 1. 1. This Mini Review deals with the metabolic consequences of administration of the hormone cortisol on proteins, carbohydrates and lipids in teleost fish. 2. 2. Many effects of administered cortisol on intermediary metabolism in fish have been reported: inhibition of protein synthesis and/or catabolism of tissue protein which result in higher availability of amino acids, induction of gluconeogenesis and of liver aminotransferases, hyperglycemia and glycogen deposition in the liver, induction of gluconeogenic enzymes, liberation of free fatty acids and deposition of liver lipids. All these effects are observed to a greater or less extent. However, the experimental data show that some effects are inconsistent. 3. 3. Some explanations for the inconsistencies are given.

The anaerobic energy metabolism of goldfish determined by simultaneous direct and indirect calorimetry during anoxia and hypoxia

SummaryThe energy flow of the anaerobic metabolism of glodfish at 20°C during hypoxia and anoxia was studied by simultaneous direct and indirect calorimetry. During anoxia the heat production as determined by direct calorimetry (180 J · h−1 · kg−0.85) is reduced to 30% of the normoxic level (570 J · h−1 · kg−0.85), which is the same reduction as found previously. The patterns of substrate utilization are compared with previous results, where the anoxic pattern was established by simultaneous calorimetry without carbon dioxide measurements. The present results, which do include carbon dioxide measurements, show the same pattern: carbohydrate and protein as substrates and carbon dioxide, ethanol and fat as end products. The pattern of substrate utilization at low oxygen levels is a combination of the anoxic pattern with an aerobic component. During anoxia only 5% of the metabolizable energy is used for energy metabolism. Of the remaining part (metabolizable energy for production) 60% is converted into ethanol and 40% into fat. At two hypoxia levels the distribution of the metabolizable energy for production into ethanol and fat is the same.

Neurotransmitter levels and energy status in brain of fish species with and without the survival strategy of metabolic depression

Abstract The effects of anoxia were studied in the whole brain of three fish species, each with a specific metabolic strategy for anoxic survival. Goldfish (Carassius auratus) combine a lactate to ethanol conversion with a metabolic depression, tilapia (Oreochromis mossambicus) use an anaerobic glycolysis with the strategy of metabolic depression, and carp (Cyprinus carpio) use an increased anaerobic glycolysis for energy production. Tilapia and carp were exposed to anoxia until they lost equilibrium and exhibited escape reactions, this occurred after 2 hours of anoxia for tilapia and 30 minutes of anoxia for carp. Goldfish were exposed to a selected period of 8 hours anoxia. The energy status and neurotransmitter (amino acid) levels in whole brain tissue were measured after anoxia exposure. The energy status was affected in all three groups exposed to anoxia. Lactic acid levels increased five- to six-fold in all three groups. No direct correlation was observed between energy status and survival strategy. Remarkably, the changes in the amino acid patterns in whole fish brains show the greatest changes in the anoxia-tolerant goldfish, an intermediate pattern in tilapia, and nearly no changes in the anoxia-intolerant carp. The changes in amino acid are probably dependent on the period of anoxia exposure. For goldfish, the lactate-ethanol conversion primarily determines anoxic survival, but the strategy of metabolic depression observed in goldfish and tilapia may contribute secondarily to anoxic tolerance. It is hypothesized that a decrease of excitatory neurotransmitters (mainly glutamate), in combination with an increase of inhibitory neurotransmitters (mainly GABA), may contribute to the process of metabolic depression and prolong survival.

Direct calorimetry on free swimming goldfish at different oxygen levels

Heat production and oxygen consumption of groups of fasting, dark acclimated free swimming goldfish were measured at 20‡C during normoxia and anoxia. For this purpose a special 1 liter flow through microcalorimeter was constructed. It appeared that the normoxic values could be established at any time 2 days after introduction of the fish into the calorimeter, 700 j/h/MW and 1.6 mmoles/h/MW respectively. The normoxic oxycalorific value of 20 kJ/l O2 indicates the use of a mixed substrate for oxidation. During anoxia, heat production was reduced to 30% of the normoxic level; 200 J/h/MW.ZusammenfassungDie Wärmeerzeugung und der Sauerstoffverbrauch von Gruppen fastender, dunkelakklimatisierter freischwimmender Goldfische wurden bei 20‡C unter normalem Sauerstoffangebot (Normoxie) und in sauerstoff-freiem Wasser (Anoxie) gemessen. Hierfür wurde ein spezielles 1-Liter-Durchfluss-Mikrokalorimeter konstruiert. Anscheinend werden die Werte bei Normoxie (700 J h−1/ Stoffwechselgewicht bzw. 1.6 mmol h−1/Stoffwechselgewicht) zu jeder Zeit später als 2 Tage nach dem Einsetzen der Fische in das Kalorimeter eingestellt. Der oxykalorische Wert von 20 kJ/l O2 deutet auf den Einsatz eines Substratgemisches bei der Oxidation unter Normoxie. Bei Anoxie vermindert sich die Wärmeerzeugung auf 30% des Wertes bei Normoxie: 200 J h−1/Stoffwechselgewicht.РЕжУМЕтЕплОВыДЕлЕНИЕ И пОт РЕБлЕНИЕ кИслОРОДА гРУппОИ хОРОшО АкклИ МАтИжИРОВАННых сВОБОРНО плАВАУЩИх ж ОлОтИстых РыБОк БылО ИжМЕРЕНО пРИ 20‡ пРИ НОРМАльНОМ У РОВНЕ кИслОРОДА И пРИ ЕгО НЕДОстАткЕ. Д ль ЁтОИ цЕлИ Был ОсУЩЕ стВлЕН ОДНОлИтРОВыИ пОтОк Ч ЕРЕж кАлОРИМЕтР. пОкАжАНО, ЧтО пРИ НОРМ АльНОМ УРОВНЕ кИслОР ОДА, ВЕлИЧИНы тЕплОт И пОт РЕБлЕНИь кИслОРОДА, УстАНОВлЕННыЕ спУст ь ДВА ДНь пОслЕ ВпУскА РыБОк В кАлОРИМЕтР, сОстАВль лИ, сООтВЕтстВЕННО 700 Дж·ЧАс−1·MB−1 И 1,6 ММОль· ЧАс−1·МB−1. НОРМАльНОЕ ОксИтЕплОтВОРНОЕ жН АЧЕНИЕ, РАВНОЕ 20 кДж/1 О2, УкАжыВАЕт НА Ис пОльжОВАНИЕ сМЕшАНН ОгО сУБстРАтА В пРОцЕссЕ ОкИслЕНИь. пРИ кИслОРОДНОМ гОлОДАН ИИ тЕплОВыДЕлЕНИЕ пО НИжАлОсь ДО 30% От НОРМАльНОгО УРОВН ь И сОстАВльлО 200 Дж·ЧАс−1·MB−1.

Direct calorimetry of aquatic animals: Automated and computerized data-acquisition system for simultaneous direct and indirect calorimetry

Abstract A system for computerized registration of heat production data and oxygen tension values of a differential 1 litre flow-through microcalorimeter (Setaram GF 108) is described. The linked values of oxygen concentration and heat production data were simultaneously stored on a computer. The aerobic and total heat production rates were thus measured of goldfish ( Carassius auratus L.) during normoxia, hypoxia and anoxia exposure. Incidentally, a partial anaerobic response was observed in goldfish during normoxia. During severe hypoxia and anoxia, goldfish respond with a reduction of the metabolic rate and a strong increase of anaerobic heat production. From the linked oxygen consumption and heat production data, the oxycaloric equivalent was calculated. The described system enables us to study continuously the effects of environmental factors on the metabolic rate of aquatic organisms.

A novel 1 liter flow-through calorimeter for heat production measurements on aquatic animals without stress

Abstract A special custom-made 1 liter differential flow-through calorimeter (Setaram GF108) has been adapted for flow-through heat flux measurements of aquatic animals. The lower limit of detection in a 1 liter vessel is 0.1 mW, whereas the sensitivity shows a linear correlation with the flow velocity up to at least 60 ml min−1. By carefully choosing the conditions and allowing enough time for adaptation, it appears to be possible to obtain data from stress-free animals. In this way the heat production of aquatic animals as a measure of total metabolic activity can be determined under aerobic or anaerobic conditions. During anoxia the heat production in goldfish falls to 30% of the nonnoxic level. This apparatus is a major breakthrough in direct calorimetry of animals, owing to the constant conditions and to its advanced electronics.

Influence of Hypoxia Exposure On the Energy Metabolism of Common Carp (Cyprinus Carpio L.)

Hypoxic conditions is a common adverse environmental condition in an aquatic environment. To study the responses of fish to this phenomenon common carp (Cyprinus carpio L.) were exposed to a graded hypoxia load and the oxygen consumption was measured continuously. At 30%AS (air saturation) 20%AS, 10%AS, 5%AS and 3%AS blood, liver and white muscle samples were collected. In the blood, haematological parameters, substrates (FFA, lactate and glucose), as well as the stress hormone cortisol were measured. High-energy phosphorylated compounds and lactate were measured in liver and white muscle tissue. During hypoxia, ATP concentrations and the adenylate energy charge (AEC) remained constant in white muscle, whereas both declined in liver tissue. The critical oxygen tension, which reflects the onset of a physiological or biochemical response at a certain hypoxia load, indicates that rapid changes were recorded in the blood, followed by the liver while white muscle (except for phosphocreatine (PCr)) is rather insensitive to environmental hypoxia. It is concluded that the impaired oxidative phosphorylation is compensated by the creatine kinase equilibrium reaction (depletion PCr pool) and the anaerobic glycolysis (lactate production).

Direct calorimetry of aquatic animals: Dynamic response of biological processes

The theory of system identification was used to determine the time constant τ of a 1 litre flow through differential calorimeter (Setaram GF 108) at a flow rate of 50 ml min−1. By numerical differentiation the impulse response function g(t), the time derivative of the step response f(t), was calculated. With the aid of the Prony method, the time constant a2 of the time-discrete system of the decimated dataset was calculated, giving a mean value of 0.7402 ± 0.0044 (n = 4). This value was converted to the time constant τ of the time-continuous system, giving a value of 33.25 ± 0.65 min (n = 4). The description of the system agreed with a model for a first order process. For control of the time constant value, the step response f(t) and the impulse response g(t) signal were simulated from the original block diagram u(t) which gave a suitable fit. Via the technique of deconvolution, the datasets of a biological case study with goldfish (Carassius auratus L.) were desmeared to describe the dynamic responses of the biological processes in the calorimetric vessel with a much reduced time constant τ. Finally, the timescale on which the process of metabolic depression takes place in this species during anaerobiosis was estimated to be several minutes.

Reversed-phase ion-paired HPLC of purine nucleotides from skeletal muscle, heart and brain of the goldfish, Carassius auratus L.--II. Influence of environmental anoxia on metabolite levels.

1. The type and the amounts of some (di)nucleotides in white skeletal muscle, heart and brain of anoxic goldfish were established with a reversed-phase ion-paired HPLC method. 2. Significant changes in the levels of these metabolites, as compared to controls, were observed. The most consistent change is the increase of IMP and of IMP-load (IMP/ATP + ADP + AMP) in the three tissues during anoxia. 3. Adenylate energy charges are maintained at a high level in the anoxic white muscle and the anoxic heart. Comparison of these results with those from conventional enzymatic methods for the quantification of (di)nucleotides showed, except for IMP, no significant differences.

Direct calorimetry of aquatic animals : effects of the combination of acidification and hypoxia on the metabolic rate of fish

Abstract The results of acidification on the metabolic rate of tilapia (Oreochromis mossambicus Peters) were studied in a differential 1-liter flow-through microcalorimeter (Setaram GF 108). After three days at pH 7.6 at normoxic conditions, the pH was slowly reduced to pH 4.0 at an acidification rate of 3.6 pH units over 240 min. Acidification during normoxia had no significant effects on the heat production ( Q ), the oxygen consumption ( V O 2 ) and the oxycaloric equivalent. Further-more we investigated whether the combination of hypoxia and acidification works synergistically. Fish were exposed to a graded hypoxia load of respectively 40% air saturation (AS), 25% AS, 15% AS and 5% AS, 8 h per level, in combination with acidification at pH 4.0. No support for a synergism was found in this study. All tilapia survived severe hypoxia (5% AS) in combination with acidification (pH 4.0) due to a metabolic depression.