ABSTRACT
The biosynthesis of polyamines has been well established in the embryonic, neonatal, and adult heart, and it displays significant changes that might be correlated to the physiological, biochemical, and ultrastructural changes occurring at the various stages of developing heart. In vitro experiments with cell-free systems have shown that polyamines might positively affect various steps involved in nucleic acid and protein biosynthesis. In accordance with this, the perfusion of isolated hearts with polyamines has been reported to increase the rate of incorporation of ribose, phenylalanine, and acetate into myocardial RNA, protein, and histone, respectively. The possible involvement of cellular polyamines in determining heart cell sensitivity is clearly supported by the fact that inhibition of polyamine accumulation leads to an improved or an impaired responsiveness to cAMP or cGMP-mediated effectors, respectively. Conversely, serum-mediated induction of TAT is completely prevented by blocking polyamine sythesis, thus suggesting that polyamine accumulation is a requirement for the cAMP-independent mechanism of TAT induction.
