Effect of malaria on rate of protein synthesis in individual tissues of rats.

The levels of total RNA and protein and the fractional rate of protein synthesis were measured in nine tissues of rats infected with malaria and compared with those of uninfected controls fed either ad libitum or the same amount of food as that eaten by the infected animals (pair fed). Apart from spleen there were no appreciable differences in any of the three aspects measured in the early part of the infection (on day 4). By day 10, however, some nonmuscle tissues from infected rats had increased amounts of RNA and protein relative to the ad libitum controls, whereas skeletal and smooth muscle both showed decreased levels. In most cases the content of RNA and protein were higher in tissues from infected rats when compared with the pair-fed controls. The rate of protein synthesis in spleen, lung, and heart of infected rats was higher or equal to that in ad libitum controls. In the other tissues it was lower. In many cases the observed changes in infected rats could not be attributed solely to a decreased food intake. The data illustrate how the response of protein metabolism to an infection differs in individual tissues, with some of them exhibiting catabolic responses and others anabolic ones.