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ACUTE EFFECTS OF OZONE ON HEART RATE AND BODY TEMPERATURE IN THE UNANESTHETIZED, UNRESTRAINED RAT MAINTAINED AT DIFFERENT AMBIENT TEMPERATURES
Citation:
Watkinson, W., A. Aileru, S. Dowd, D. Doerfler, J. Tepper, AND D. Costa. ACUTE EFFECTS OF OZONE ON HEART RATE AND BODY TEMPERATURE IN THE UNANESTHETIZED, UNRESTRAINED RAT MAINTAINED AT DIFFERENT AMBIENT TEMPERATURES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-93/089 (NTIS PB93175586), 1993.
Description:
The present studies were conducted to investigate the concentration-response characteristics of acute ozone (O3) exposure on the cardiovascular and thermoregulatory function of the unanesthetized, unrestrained rat, and to examine the modulating effects produced by changes in ambient temperature (Ta) on the induced toxic response. For all studies, groups of male Fischer 344 rats (n=4-6/group) were implanted with radiotelemetry transmitters and allowed to recover overnight. The transmitters permitted continuous monitoring of electrocardiogram (ECG) and body core temperature (Tco); heart rate (HR) was derived from the ECG signal. Frequency of breathing (f) wag obtained in selected experiments by means of a Fenn box. All animals were monitored according to the following protocol: control (filtered air; 0.25 h); exposure (03; 2 h); recovery (filtered air; 3-18 h). For the concentration-response experiments, O3 concentration wag varied from 0.25-1.0 ppm and all exposures were conducted at an Ta of 18-20 degrees C. Significant decrease in HR and Tco were demonstrated at 03 concentrations ag low ag 0.37 ppm. To investigate the influence of Ta on the O3-induced response, a second series of experiments was conducted according to the above protocol using a single O3 concentration of 1.0 ppm. Two groups of rats were used for these experiments. The first group of rats was maintained at an Ta of 18-20 degrees C throughout the experiment and exhibited an average 3.6 degrees C drop in Tco accompanied by a 185 bpm decrease in HR.