Metabolism of 1-14C-ornithine and 1,4-14C-putrescine in chronically uremic and control rats.

The metabolism of ornithine and putrescine was studied in vivo in chronically uremic and control rats. Rats were injected intraperitoneally with 1,4-14C-ornithine or 1,4-14C-putrescine and expired 14CO2 was collected for 4 hr. After injection of 1-14C-ornithine. 14CO2 expiration was decreased in uremic rats as compared to controls. Conversely, after 1,4-14C-putrescine injection, expiration of 14CO2 was increased in uremic rats as compared to controls. Four hours after the injection of 1-14C-ornithine, there was more radioactivity in liver and muscle and less radioactivity in kidney of uremic rats as compared to the respective sources in control rats. In uremic rats, 4 hr after 1,4-14C-putrescine injection, the radioactivity retained in the muscle and plasma was greater than in corresponding sources in control rats; whereas the radioactivity retained in uremic liver and kidney was similar to that of control rats. The greater putrescine-derived radioactivity retained in uremic tissues reflects either the retention of injection racer compounds, or retention or decreased catabolism of putrescine metabolites. From 14CO2 expiration data obtained, it appears that ornithine catabolism is reduced while putrescine catabolism is increased in uremia.