Cardio-respiratory effects of chloramine-T exposure in rainbow trout

Abstract

In order to establish whether the blood gas respiratory disturbances noted with exposure to chloramine-T are due to differences in the rates of uptake of O2 and excretion of CO2 or gill blood flow, adult rainbow trout (Oncorhynchus mykiss) were fitted with dorsal aorta and bulbus arteriosus catheters to facilitate blood pressure recordings, an ultrasonic blood flow probe and opercular impedance electrodes. Fish received either a 45-min static exposure to 9 mg l−1 chloramine-T or tap water (control) and continuous recordings of blood pressure, and ventilation frequency and amplitude were made. Pre- and post-exposure arterial and venous blood samples were taken and analyzed for O2 and CO2 content, hemoglobin concentration and hematocrit. Chloramine-T exposure had no effect on any of the continuously recorded parameters. However, individual measurements (made immediately prior to and following exposure) of cardiac output and O2 uptake rates increased significantly following exposure to chloramine-T compared to before exposure. CO2 excretion rates were unaffected by chloramine-T exposure. Calculation of the perfusion convection requirement showed a significant increase for CO2 but not for O2. It was concluded that increases in O2 uptake resulted from increased cardiac output but that CO2 excretion, a diffusion-limited process, was not increased due to additional diffusive limitations caused by the irritant effect of chloramine-T.