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Groups of rainbow trout (Salmo gairdneri, Richardson) were continuously swum at 20 cm s-1 (1.0 body lengths s-1) for 0, 3, 30, and 200 days. No significant changes in fish condition factor, combined red and white muscle mass, muscle fibre size or fibre size distribution were observed. After 200 days of swimming there was a significant 2.2 fold increase in red muscle mass. Number of capillaries per red muscle fibre increased significantly in each group by a maximum of 27% after 200 days exercise. Number of capillaries per white muscle fibre increased significantly by 95% after 200 days exercise. Blood lactate, haemoglobin (Hb) concentration haematocrit, erythrocyte adenosine triphosphate, and whole blood oxygen affinity P50 were unchanged by swimming. After 30 and 200 days swimming there was a shift in expression of white muscle lactate dehydrogenase (LDH) isozymes from LDH-A to LDH-B. Within the duplicated LDH-B isozyme complex, there was a shift in expression from LDH-B to LDH-B' subunits. These results suggest that sustained swimming at 1(-1) bl s-1 increased the aerobic capacity of red and particularly white (fast) muscle of rainbow trout but did not alter the gas transport characteristics of the blood.

Qualitative changes in haematology and blood chemistry of the giant Antarctic cod, Di.s.soslichus mawsoni, were followed during recovery from the stresses of capture and cannulation under MS 222 anaesthesia. Cannulation with anaesthesia resulted in a transient rise in haematocrit and haemoglobin concentration, and a fall in blood pH. These changes returned to stable values 8-24 h later. Blood lactate and mean corpuscular haemoglobin concentration remained near to resting values. Severe stress following -12 h on a set line resulted in a more marked increase In haemoglobin and haematocrit and decrease in pH. Moreover, the erythrocytes appeared swollen and blood lactate was appreciably elevated. The blood profile returned to stable values some 24 to 70 h after capture. Changes in blood ATP were noted in severely stressed fish. Experiments with the smaller nototheniid species, Pagothenia bovchgrevinki. indicated that erythrocyte swelling, elevated blood lactate, and changes in ATP concentration were delayed manifestations of severe agitational stress. The significance of these findings is discussed in relation to oxygen transport in fish having low metabolic rates, and also in relation to widely used techniques for sampling blood.

Acute exposure of rainbow trout to hypoxic water (PwO2 = 40 mmHg, 15 degrees C) caused a significant (P less than 0.01) increase in blood O2 affinity, from the normoxic P50 value (at pHc 7.93) of 23.2 +/- 1.1 mmHg to about 19 mmHg, within 5 min. Specimens injected with the beta-antagonist propranolol showed no change in blood P50, despite a more pronounced reduction of arterial PO2 during the hypoxic exposure. The change in blood P50 coincided with an increase in plasma catecholamines, notably noradrenaline. There was no change in the molar ratios of ATP:Hb4 and GTP:Hb4. The altered blood P50, however, correlated with an alkalinization and an increased sodium concentration of the red cells. This red cell alkalinization can be explained by beta-adrenergic stimulation of a membrane bound Na+/H+ antiporter. Propranolol injection into normoxic resting trout caused a significant decrease in PaO2 and increase in PaCO2 indicating beta-adrenergic control of gas exchange in the gills.

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An application of a gas chromatography/isotope ratio mass spectrometry (GC/IRMS) method for stable carbon isotope analysis of blood plasma lactic acid is presented. The method involves a simple extraction procedure followed by derivatization with diazomethane. It is shown that derivatization is by single methylation, thus minimizing the dilution of the derivative's 13C content, yet still ensuring good chromatographic behaviour on a polar capillary column. This ensures a high sensitivity of the isotopic analysis. Repeatability, expressed by the coefficient of variation, varied from 0.3% to 19%, depending on sample enrichment. Reproducibility was 2.3% over a 10 day period. The detection limit, defined as 2SD, was about 0.0004 atom % excess (APE), equivalent to 0.001 mol % excess, when based on a measured precision of about 0.2/1000 in delta notation. A comparison is made between enrichments obtained using a calibration curve and those obtained using a correction for the added methyl carbon. The two methods agreed well, with a relative difference (delta APE/APE x 100%) of less than 0.5% for samples enriched with between 0.004 and 1.28 APE. It is concluded that the method provides simple and precise isotope analysis of picomole quantities of blood lactate.