[Additional findings on age differences in the blood circulation in rats]

By means of microparticles labelled by radioactive strontium 85Sr (3M, USA) the authors in two experiments established cardiac output and local blood flow through bones and certain other organs and tissues of rats in two distinct age categories (35 and 90 days, 45 and 110 days). The results of both experiments showed 1) significant decrease of blood flow in skull, lumbar vertebrae, distal epiphysis, distal metaphysis and thighbone diaphysis and tibia in older rats of both sexes (proof of previous results with 86Rb), 2) constantly significant decrease of blood flow through a skin sample taken from the ventral side of the trunk and 3) nonconstant increase of blood flow through kidneys of older rats. The causes of observed changes are not known, physiological importance to be supposed particularly as regards the circulatory changes in bones, is also not clear.