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Changes in expression and CRE binding proteins of the fibronectin gene during aging of the rat.

The level of plasma fibronectin (pFNT) which is synthesized in the liver and secreted to the plasma has been found to decrease with age. Nuclear run-on transcription, slot-blot, and northern blot analysis also show that the expression of the FNT gene is lower in the liver of old rats. cAMP is known to influence the expression of the gene. Gel mobility shift assay using an oligonucleotide containing the cAMP responsive element (CRE) and nuclear extract of liver shows the presence of trans-acting factors that bind to CRE. These factors change with age. This may be the reason for the lower expression of the gene in the old rat.