Continuous determination of blood volume on conscious rats during water and food intake

A method to measure circulating blood volume continuously on a conscious rat was developed using the dilution method of 51Cr-labelled red cell and changes in blood volume after drinking and food intake were monitored. In splenectomized rats, the blood volume showed a transient decrease of 0.1-0.2 ml/100 g body wt. about 30 min after food intake, while increasing by 0.1-0.4 ml/100 g body wt. after water ingestion. Thus, blood volume showed fluctuations following water and food intake ranging from 2-8% of the circulating blood volume.