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METABOLIC RATE AS A FUNCTION OF AGE IN BROWN NORWAY AND LONG-EVANS RATS.
Citation:
GORDON, C. J. AND B. L. BISHOP. METABOLIC RATE AS A FUNCTION OF AGE IN BROWN NORWAY AND LONG-EVANS RATS. Presented at Federation of American Societies for Experimental Biology (FASEB) Meeting (Experimental Biology Meeting), Anaheim, CA, April 24 - 28, 2010.
Impact/Purpose:
Understanding how metabolic rate (MR) varies with age is critical for the development of pharmacokinetic models of environmental toxicants in aged animals. Male rats of the BN and Long-Evans (LE) strain were housed unrestrained inside a direct calorimeter maintained at a ambient temperature of 22°C for three hours while dry and evaporative heat loss were monitored continuously
Description:
Brown Norway (BN) rats are commonly used in aging studies but relatively little is known on their metabolism as it varies with age. In fact, there is considerable disagreement on the wholebody metabolism of aging rats with some studies indicating a decrease and others showing an increase with advanced age. Understanding how metabolic rate (MR) varies with age is critical for the development of pharmacokinetic models of environmental toxicants in aged animals. Male rats of the BN and Long-Evans (LE) strain were housed unrestrained inside a direct calorimeter maintained at a ambient temperature of 22°C for three hours while dry and evaporative heat loss were monitored continuously. The sum of dry and evaporative heat loss was averaged over the final hour in the chamber to calculate metabolic rate in dimensions of Wlkg. MR was measured in rats ranging from 1 to 23 months of age in BN rats and 1 to 12 months in LE rats. MR of both strains was -25 W/kg at 1 mo and then dropped rapidly with aging and growth. MR of both strains reached an asymptote from an age of 4 months and beyond; throughout this period, MR of the BN and LE strains was approximately 7 and 5 Wlkg, respectively. There was no indication of an increase with MR as rats approached senescence. Body weight of the LE strain at maturity was approximately double that of the BN strain. While body weight has a marked effect on MR, there were strain specific differences in MR that were independent of body weight. This is an abstract ofa proposedpresentation and does not necessarily reflect EPA policy