Investigation of selected variables from the primary and secondary circulatory systems in rainbow trout (Oncorhynchus mykiss)

A series of experiments are reported which utilize a cannulating method for the secondary circulation. A modification of a new method for cannulating the secondary system in rainbow trout (Oncorhynchus mykiss) is described. A T-shaped catheter was placed inside the lateral cutaneous vessel, thereby allowing multiple samples to be taken from the same animal. Rainbow trout were cannulated in both the primary and secondary circulatory systems. Repeated samples were taken over several days to determine the concentrations of selected parameters. White blood cell numbers were significantly greater in the secondary system; however, they also varied much more than the cell numbers in the primary circulation suggesting that blood cell composition changes within the secondary circulation. Concentrations of selected parameters from the secondary circulation were calculated as a percentage of the primary system: plasma cortisol was 60.2 ± 9.7%; total protein was 72.9 ± 4.9%,plasma glucose was 90.3 ± 11.4%, plasma chloride was 97.8 ± 1.9%, and hematocrit was 0.5 ± 0.2%. Only glucose and chloride concentrations did not differ significantly between the two systems. Adrenaline was determined to be 64.9 ± 17.3% in the secondary compared to the primary circulation; however, since this hormone was detectable in only a few samples, this value may not be representative of the system. A sharp increase in the cortisol concentration of the primary system 48 hours after operation was observed again approximately two hours later in the secondary system, suggesting a slow mixing time between the primary and secondary circulation. Fish were vaccinated with an intraperitoneal injection of Vibrio anguillarum to investigate the possible role of the secondary system in immune function. As in the first experiment, the white blood cell numbers were significantly greater and more variable in the secondary compared to the primary circulation. The concentrations of selected plasma constituents in the secondary system were also determined as percentages of the primary circulation: lysozyme was 114.9± 14.9%, cortisol was 51.4 ± 17.2%, total protein was 71.1 ±7.5%, glucose was 92.1 ± 11.8%, and chloride was 96.4 ±2.3%. Only total protein was significantly different between the two circulatory systems. A low response in the hemolytic plaque assay and a negative outcome from antibody titer tests in both circulatory systems, suggests that the adaptive (specific) immune response may not have been stimulated.Land and Food Systems, Faculty ofGraduat