| Popis: |
The recent finding (Chen et al. , BBA, 312, 598, 1973), that albumin synthesis is 50% higher in isolated old rat liver microsomes than in young rat liver microsomes, has led us to investigate the mechanism responsible for this age-related, change. Purified polysomes were isolated from young and old rat livers and their sedimentation patterns were analyzed. The polysome profiles obtained for the young and old preparations were almost identical. Differences in the relative amounts of albumin-synthesizing polysomes in the young and old polysome fractions were detected in two ways. (1) The extent of specific binding of 125I-anti-rat serum albumin to those polysomes synthesizing albumin was measured. It was found that more 125I-anti-rat serum albumin bound to old rat liver polysomes than to equal amounts of young rat liver polysomes. (2) Albumin-synthesizing polysomes were directly precipitated from both young and old total polysome population using two different immunological procedures. The results showed that more albumin-synthesizing polysomes were precipitated from old rat liver polysomes than from equal amounts of young rat liver polysomes. This evidence suggests that there is an increased amount of messenger RNA coding for albumin in the total polysome fraction of old rats when compared to young rats. |
