Radiochromium distribution in aged rats.

Fragmentary studies suggest that tissue chromium (Cr) levels decrease with age. Regardless of the mechanism for such a decline, decreased tissue exchange with administered radiochromium (51Cr) should result. Accordingly, body retention, urinary excretion, and serum (plasma) and tissue levels of 51Cr were determined in 2-month-old male control rats and in 9-18-month-old experimental male rats 3 days after the intravenous injection of high specific activity trivalent 51Cr. The older rats retained relatively less 51Cr than the 2-month-old rats in comparison to body weight but had similar urinary excretions of 51Cr. Serum (plasma) 51Cr levels were generally higher and tissue 51Cr levels generally lower in the older rats, with the exception of spleen 51Cr content, which increased. Skeletal 51Cr content was markedly decreased, by 30-85%. These data suggest that aging alters 51Cr distribution by decreasing cellular Cr content and transport. Other mechanisms must be operative in bone since skeletal Cr is primarily extracellular.