Changes in size, DNA content, and nuclear ploidy of rat liver produced by the environmental microflora

Effects of the environment microflora on rat liver were studied in the present investigation. Rats born under sterile conditions were bred either in a germfree or in a "SPF" environment. At 12 weeks of age the liver of the SPF rats was larger by 20% and contained more DNA than germfree rat liver. Volume analysis, by means of a particle counter, of isolated nuclei suggested that the increase of DNA was due to an increase of hepatic nuclear ploidy. The findings show that infections may influence liver size and ploidy. They indicate that the state of infection should be controlled in animal studies which concern the regulation of liver growth and ploidy or which use liver weight and DNA as reference standards.