[Effect of reduced caloric intake on circadian rhythm of gas exchange and heat production in old rats].

Fifty male Wistar rats at the age of 24 months were divided into two equal groups (test and control). Test animals received a 2-fold reduced ration. At the age of 32 months all the animals were examined for gas exchange and heat production circadian rhythm. The test animals were 3 hours fast compared to controls in maximal values of gas exchange, rectal temperature and heat conductivity, while relevant mean daily values did not change. The circadian rhythm of the above values in test animals corresponded to that of younger rats indicating higher performance of the underlying mechanisms and explaining longer survival of the test rats, who had less rates of gas exchange and rectal temperature variability and lower heat circulation coefficient.