Brodeur, Julie C.2006-07-282006-07-2820002000http://hdl.handle.net/10012/472The objectives of this study were to examine the responses of teleost cardiac function to selected environmental contaminants, and to determine how changes in cardiac output relate to energy metabolism. When exposed for 24 h to concentrations representing SO % and 25 % of the 96 h-LCS0 of pentachlorophenol (PCP) and tetrachloroguaiacol (TCG), rainbow trout (Oncorhynchus mykiss) exhibited a reduction of oxygen consumption to about 50-60 % of basal levels while their cardiac output remained stable. The absence of variation in cardiac output probably originated from the fact that arterial oxygen content was maintained stable during the impairment of oxygen utilization by the chlorophenols; there was therefore no stimulus or need for an increase in convective oxygen delivery. In another series of experiments, adult Atlantic salmon (Sa/mo solar) were exposed for 48 h to water from the acidified (pH 5.2) Fossbekk River (Norway) with or without a nominal concentration of either SO, 7S, 100, or 12S μg•L· 1 of aluminium (Al) added as AlCh, or to circumneutral water (pH 6.6) from lms River (Norway). Most of the fish died before the end of the 48-h exposure period when exposed to Fossbekk River water + 12S μg Al•L-1, while no mortality was observed in the other treatments. Exposure to Fossbekk River water with 75, 100 and 12S μg•L· 1 of Al caused a reduction of cardiac output to about 70-7S % of basal levels, primarily through a decrease in stroke volume. A large elevation of heart rate was observed at 12S μg Al•L·1, but such a tachycardia was not evident with the other concentrations of Al. The incapacity of the tachycardia to elevate cardiac output and the subsequent death of the fish at the highest Al concentration suggest that this response is more of a maladaptative reaction than a compensatory or adaptative reaction. Cardiac output returned to basal levels within 36 h when the water pH was raised to 5.8 by adding CaCO3 at the end of the 48-h exposure period. By that time, plasma concentrations of sodium and chloride had started to return to basal levels and haematocrit was back to nonnal, but none of the other altered blood parameters (pH, HCO3·, potassium, glucose) had started to recover. The comparative dynamics of the alterations in blood chemistry and cardiac output suggest that the decrease in cardiac output was the result of the increase in haematocrit and the reduction in plasma volume resulting from the osmotic shifts associated with the ionic losses. In a different experiment, the effects of Al and acidic water on cardiac output were examined after fish had time to acclimate to the presence of Al and their haematocrit and plasma ion concentration had returned to baseline. Atlantic salmon (Sa/mo sa/ar) were exposed for 36 days to water from the Fossbekk River (pH 5.2) with 50 μg•L·1 of Al added as AlCh, or to circumneutral water from Ims River (pH 6.6). The resting cardiac output of the fish exposed to Fossbekk River water+ Al was not significantly different from the fish exposed to Ims River water. The growth rate of the fish exposed to acidic water was reduced after their food consumption had returned to normal levels, and their swimming activity was increased throughout the exposure to acidic water and Al. These results suggest that basal metabolic rate was not affected by the exposure and that the decrease in growth rate was predominantly the result of the increase in swimming activity. Another possible explanation is that the increase of basal metabolism, if present, was mainly the result of an increase in blood oxygen extraction rather than cardiac output. The last series of experiments indeed showed that the relative contribution of cardiac output and blood oxygen extraction to increases in oxygen consumption can vary depending on the factors affecting metabolic rate. This was concluded after examining the correlation of cardiac output, heart rate, and tissue blood oxygen extraction to oxygen consumption in fish subjected to either an acute increase or decrease in water temperature, or to an increase in swimming speed.application/pdf4478991 bytesapplication/pdfenCopyright: 2000, Brodeur, Julie C.. All rights reserved.Harvested from Collections CanadaDoctoral Thesis