Ozone toxicity in the rat: part ii. modeling changes due to ambient
temperatures and duration.
Highfill, Jerry W., and William P. Watkinson.
Biostatistics Branch, Research Support Division and Pulmonary
Toxicology Branch, Environmental Toxicology Division, Health Effects
Research Laboratory, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina 27711
APStracts 2:0547A, 1995.
Previous studies involving exposures to xenobiotic agents have
demonstrated decreases in physiological parameters such as heart rate
(HR) and body core temperature (TCO) and have shown that these toxic
responses are modulated by changes in ambient temperature (Ta). We
recently published the results of a study in which male Fischer 344
rats were implanted with radiotelemetry transmitters that permitted
continuous monitoring of HR, TCO, and motor activity. These animals
were divided into nine treatment groups (n=4-5/group) composed of
combinations of one of three O3 exposure regimens (0.0 ppm O3 x 24
h/d x 5 d, 0.5 ppm O3 x 6 h/d x 5 d, or 0.5 ppm O3 x 23 h/d x 5 d) at
one of three Ta's (10, 22, or 34oC). We now report on statistical
approaches for the modeling and analyses of these data. The models
utilized were dependent upon the treatment combinations. Circadian
rhythms of TCO during air control periods were fit by cosine models.
Overall effects of O3 in the 6 h and 23 h exposure groups were best
modeled by modified damped-sine and one compartment models,
respectively, for both HR and TCO. These results demonstrate improved
methods for the evaluation of biorhythmicity.
Received 30 December 1994; accepted in final form 7 December
1995.
APS Manuscript Number A1379-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 December 95