DIFFERENTIAL CHANGES IN TRANSFORMING-GROWTH-FACTOR-BETA ISOFORM EXPRESSION DURING POSTNATAL CARDIAC GROWTH

Transforming growth factor-beta (TGF-beta) is synthesised as an inacti ve precursor protein; this is cleaved to produce the mature peptide an d a latency associated protein (LAP), which remains associated with th e mature peptide until activation by LAP degradation. Isoform specific antibodies raised against the LAPs for TGF-beta(2) and -beta(3) were used to determine the myocardial levels of LAP (activatable TGF-beta) and full length precursor (inactive TGF-beta) forms during post-natal development in the rat. TGF-beta(2) was present predominantly as the p recursor in 2 day old myocardium. There was an age-dependent shift fro m precursor protein to LAP between 2 and 28 days. A corresponding incr ease in the level of mature (activatable) TGF-beta(2) was found. TGF-b eta(3) was detected in significant quantities only as LAP. However, a four-fold increase in the expression of TGF-beta(3) LAP was observed b etween 2 and 28 days. The substantial increases in activatable forms o f TGF-beta(2) and -beta(3) that occur in myocardium during the first 2 8 days of life in the rat support a role for these proteins in post-na tal cardiac development. (C) 1998 Academic Press.