Mikko Nikinmaa

Environmental perturbations of oxygen transport in teleost fishes: causes, consequences and compensations

Aquatic environments exhibit large spatial and temporal variations in physico- chemical factors that influence the physiology of fishes. Environmental changes in O2 and CO2 tensions, temperature, salinity, acidity, and input of toxic substances can be of both man-made and natural origin. Oxygen-depleted waters, for instance, occur naturally in habitats with heavy degradation of organic matter. Anthropogenic activity has expanded the number of environments with ‘extreme conditions’, and has created new environmental problems. Periodic or chronic oxygen depletion resulting from eutrophication is now a well-known phenomenon in many freshwater and coastal areas. Combustion of fossil fuels (emitting nitrogen and sulphur oxides) has acidified many freshwater ecosystems. Furthermore industrial activity has increasingly contaminated waters with toxic substances.

The blood oxygen binding properties of hypoxicSalmo gairdneri

SummaryThe blood oxygen binding properties of rainbow trout responded to environmental hypoxia (the oxygen saturation of water 30% at 11°C) in three ways. The quickest response was a moderate acidosis, leading to slightly lowered blood oxygen loading due to the Bohr effect. The second response, an increase of blood oxygen carrying capacity, was completed with 6 h from the onset of hypoxia. The speed of the response suggests that the formation of new haemoglobin played no practical role, the increase being caused either by a decrease of plasma volume or the liberation of erythrocytes from a storage organ. The slowest response, a 25% increase of the blood oxygen affinity within a week of hypoxia, was probably caused by the concurrent decrease of the erythrocyte ATP concentration from 4.45 to 2.51 μmol/ml erythrocytes.

Anion movements across lamprey (Lampetra fluviatilis) red cell membrane.

Chloride and bicarbonate movements across lamprey red cell membrane were investigated. The halftime for equilibration of radioactive chloride across the red cell membrane was 2.46 h, and apparent permeability for chloride-36 was approximately 10(-9) cm X s-1, a value similar to that observed for lipid bilayers. Chloride movements were not affected by the anion exchange inhibitor, 4,4-diisothiocyano-stilbene-2,2-disulfonic acid (DIDS). Furthermore, intracellular buffering is effectively isolated from the extracellular compartment, as shown by the fact that practically no pH recovery occurred in the unbuffered extracellular medium after either acidification or alkalinization. These observations show that lamprey red cell membrane is quite impermeable to bicarbonate and other acid/base equivalents.

Hauling stress in brown trout (Salmo trutta): Physiological responses to transport in fresh water or salt water, and recovery in natural brackish water

Abstract Brown trout were transported in dilute NaCl (0.6%) or fresh water, and allowed to recover in natural brackish water (salinity 0.6%). Transport in fresh water caused an increase in blood haemoglobin concentration, and decreases in mean cellular haemoglobin concentration, plasma osmolality, hyperglycaemia, muscle fat and liver glycogen content. Although present, these changes were markedly smaller in the animals transported in NaCl solution. Recovery in brackish water abolished the differences between the two groups, and the physiological parameters reached a steady-state level within a week of recovery.

Physiological changes in trout (Salmo gairdneri) during a short-term exposure to resin acids and during recovery

Six rainbow trouts were exposed to a 2 mg/l concentration of resin acids for 24 h. The toxicants influenced respiration by causing a decrease in arterial P02, red cell volume and pH, and an increase in ATP/Hb ratio. These responses were reversible on recovery. A disturbance in hydromineral balance was shown by a decrease in plasma chloride concentration, which was reversible in all but one fish. This fish had additional metabolic difficulties as shown by increases in plasma lactate concentration and enzyme activity. An indication of liver dysfunction was the increase in plasma bilirubin concentration, continuing throughout recovery.

Metabolic effects of dehydroabietic acid on rainbow trout erythrocytes

Oxygen consumption and ATP concentration were measured in rainbow trout erythrocytes incubated in a physiological saline containing 0, 5, 15, 30 or 60 mg/l dehydroabietic acid. DHAA caused a decrease in cellular ATP level and oxygen consumption at concentrations above 15 mg/l. Haemolysis increased markedly, when the cellular ATP concentration decreased below 1 mM. These data suggest that increased breakdown of red cells may be the primary reason for jaundice which is observed in resin acid-toxicated fish.

Blood volume of Salmo gairdneri: Influence of ambient temperature

Abstract 1. 1. The plasma and blood volumes of rainbow trout were determined at 7, 11 and 16°C. 2. 2. Although the plasma volume increased slightly with increasing temperature, this change was inadequate to explain the marked decrease in the blood haematocrit value and haemoglobin concentration, as measured from the dorsal aorta. 3. 3. The blood volume remained relatively unchanged. 4. 4. The decrease in the blood haematocrit value without a change in the blood volume would be explained, if the proportion of red cells travelling through the tissue capillaries were increased with rising temperature.

The role of gills in the responses of Salmo gairdneri during moderate hypoxia

Abstract 1. 1. Gill function of rainbow trout, cannulated permanently to both ventral and dorsal aortae, was studied during moderate, short term hypoxia (5.5 mg/1) at 9° 2. 2. Hb concentrations and Hct values were significantly and MCHC slightly higher in the dorsal aorta. 3. 3. P O 2 difference between the aortae decreased from 11 kPa in normoxia to 6 kPa in hypoxia. 4. 4. Blood pH as well as protein and inorganic ion concentrations of the plasma were the same in both aortae and remained constant. 5. 5. Lactate concentration in the ventral aorta exceeded that of the dorsal one in the prehypoxic fish, but decreased to same value during hypoxia.

How does environmental pollution affect red cell function in fish

Abstract The present article reviews the effects of environmental pollution on ion transport, metabolism and shape of teleost red cells. Catecholamines liberated into the blood stream in acute stresses activate sodium/proton exchange across the red cell membrane causing red cell swelling. The exchanger is inhibited by alkyltin compounds and by methaemoglobinaemia. Amphiphiles increase the potassium permeability of the red cell membrane. Exposure to lead inhibits and exposure to tetrachloro-1,2-benzoquinone activates red cell δ-aminolevulinic acid dehydratase. Resin acids, cadmium, lead and oxidizing agents such as monochloramine induce the appearance of abnormal cell shapes. In addition, environmental contamination is often accompanied by an increased frequency of micronuclei in the red cells. Specifically, this effect has been observed during exposure to benzo(a)pyrene. These, and other, examples show that many red cell parameters respond to environmental pollution. Thus, determinations of red cell ion concentrations, microscopic examination of red cells and assays of red cell enzyme activities could be a useful addition to conventional pollution monitoring studies.

Species differences in the adrenergic responses of fish red cells: studies on whitefish, pikeperch, trout and carp.

The occurrence and pH dependence (pHe 7–8) of the adrenergic red cell responses of two salmonids, trout and whitefish, and a percinid, pikeperch were studied. These are all species that live in well-oxygenated waters. The responses were compared to those of carp, which tolerates oxygen-deficient waters.The adrenergic responses of trout and whitefish red cells were pronounced. In these species red cell swelling, the accumulation of sodium and chloride in the cell, and the increase in red cell oxygen content at atmospheric oxygen tension were maximal at pH 7.3. In contrast, pikeperch red cells responded to β-adrenergic stimulation only at extracellular pH 7.1. In carp, the adrenergic response, occurring below extracellular pH 7.5, was small as compared to the two salmonids. In each case the onset of the adrenergic response coincided with the onset of the Root effect.The differences in the adrenergic responses between the two salmonids and pikeperch suggest that the occurrence of the adrenergic response is not directly related to the environmental oxygen requirements of the species, but may be linked to the activity pattern.