Species differences in the deoxyribonucleic and ribonucleic acid contents of livers of non-pregnant and pregnant mice, guinea-pig and cats.

Abstract

1. The protein content of liver cells is almost independent of the size of the animal (mice, cats and previous results on rats, Campbell & Kosterlitz [1949]), and varies with the amount of protein eaten. 2. As has already been shown for rats, the ribonucleic acid ('RNA') content of the liver cells of non-pregnant mice, guinea-pigs and cats varies directly with the protein content of the cells. For a given protein content the mouse and rat have more RNA than the guinea-pig and cat. 3. During pregnancy there is a rise of the deoxyribonucleic acid ('DNA') content of the livers and in the protein content of the liver cells of mice (and rats), but not of guinea-pigs. 4. An excess of RNA over that predicted from the protein content of the liver cell has previously been found for the rat during pregnancy, and ascribed to the action of a placental factor on the maternal liver. A similar excess of RNA has now been observed in the mouse and, to a less extent, in the guinea-pig. It appears to be absent in the cat. 5. Possible causes of some of these species differences are considered.